Shorting on 88E, page-89

If you are putting orders in at market, then you can benefit from centrepoint as asx's matching engine can match Commsec's order with someone else. They "jump the queue" because they are willing to pay more/accept less than the best bid/offer in the lit markets.
If you are putting in limit orders, then you can't benefit (unlikely at least). Also, no-one can put in a half-step limit - that isn't a thing. You'll also find that Commsec routes your trade to the place where it can get best execution, which means potentially both CBOE and ASX. Unless you're doing direct market access with no smart order routing, I'm guessing you don't.