ok serious question this time

i'm just curious... how come at the end of the trading day (according to comsec market depth) - at the end of the day, after close at 4pm but before after hours adjustment between 4pm and 4.10pm, there are always a couple of purchases at just a half a cent or a cent more than last bid and these always get filled...? is it in anticipation of a big open the following day? those orders could have been filled throughout the trading day at less than close presumably...