Genius! @Exlpore Thank you for the insight.

Oh hang on.... last traded price was $0.103

Would you know the next cutoff price? That is, when it would stop me from trading at 0.5cent increments.

I reckon what you are missing there is that the 0.1c increments ($0.001) only goes up to 10 cents, and after 10c the increments are half a cent ($0.005) not one tenth of a cent - see the right side of your Market Depth table.

And you're trying to place an order at $0.101, which is above 10c where the one tenths of a cent increments are not allowed by the ASX.

You will occasionally see stocks rise or fall by strange amounts, like 7 tenths of a cent, but my understanding is that is either due to Chi-X allowing smaller increment trades than the ASX does, and/or volume matching where a mid-point is used between a buy and a sell price for certain trades where such mid-points can be used - this only applies to institutional trades as I understand it (the volume matching using mid-points) where the relevant permissions are in place for the modifications of those trades by the system. For ordinary retail investors trading on the ASX, it's 0.001 increments up to 10c, then half cent increments from 10 cents up.

Additional: I was too late! I see this question has already been answered. Regarding where the half cent increments end, I thought they did end somewhere, but I've just checked the trade history for CSL today, and there has been the occasional trade gone through this morning at half a cent increments - not many at all - but they do exist. Not sure if there is a limit imposed on placing trades at half cent limits above a certain dollar value though. I don't think I've ever tried to place a trade at a price like $20.005 or $101.015. Perhaps someone else knows about the upper dollar value limit for half cent increments - if there is one.

Regarding that $0.103 last price for VR1 @Hands - this might explain that:

I've highlighted that trade, which was at 11:14am Sydney time, and was a Chi-X trade (CXA) not an ASX trade, and it was for 10.25 cents/share, however your online broker platform has rounded that to $0.103 (instead of $0.1025). It's either because Chi-X allow smaller increment trades or it's because of Chi-X matching up 10,000 shares on the sell side and the buy side and settling them for a mid-price (between $0.10 and $0.105) as I explained in my previous forum post on this. This won't happen on the ASX with normal retail trades, but can happen with some institutional trades as I understand it.

@Bear77 - 2nd Genius of the day! Thank you for your ever detailed insights. I feel so privileged to have my squeaks and bumps answered so quickly and seriously.

So it looks like there is some professional trading house action on VR1 today.

Possibly @Hands - however that trade value (total value) was only $1,025, and that seems a pretty small trade for a professional trading house, unless they are acting on behalf of a client who wants to accumulate a small position using smallish trades so as not to move the SP too much. A lot of the other trades (at "normal" prices) may also be from the same trading house. Many of those guys pay a monthly fee to trade, so the number of trades they make doesn't matter to them, as their fees (for trading) don't change, so they can buy or sell using many small trades and it costs them no more.

The other possibility is that it's an option that Chi-X provide to everybody if they opt in. One way it might work is that they may ask you when you place a trade if you end up at the top of the bids and the lowest offer is at the next available price point, are you happy to meet that seller in the middle. If they have a seller who agrees to sell at a quarter of a cent lower than their offer price, then the trade is done at the mid-point. I have no idea if Chi-X is offering such a service, but if they are it would explain such trades.

And there's always the possibility that Chi-X simply allow smaller increment trades to be placed. Again I don't know because I don't trade on Chi-X.

What do CX, CXXT, and NXXT mean? (commsec.com.au)

So this does happen on the ASX as well as on Chi-X - see the following:

The NXXT trades highlighted in the yellow are ASX trades and the orange circled CX trade is Chi-X - here's what Commsec says about those codes:

That's a lot of nuances here.

1) There are a lot of trades happening on platforms other than the one I see, for increments that I'm not aware of. This might help explain why I see some pretty jagged jumps at times.

2) There is a good 0.5% difference between 9.9cents and 10.5cents for a pennystock. Might explain why it is hard to tip the 10cent barrier and might explain why some penny stocks like to consolidate, to rise above that anomaly in the system.