it sounds like the NAB trading platform you are using is a bit restrictive - might be worth thinking about changing to a different online broker. I use the bog-standard online commsec account and I can definitely place buy and sell orders in fraction of cent increments. I've also never had a problem changing my orders to match the market depth (as per your problem of "Market Manipulation" above). After hearing your problems with NAB as an online broker, I'm not surprised that Commsec has such a large market share! (Hope someone from NAB reads this and takes notice)
All the best,
StatsMan
PLV Price at posting:
99.5¢ Sentiment: Buy Disclosure: Held