current trading pattern, page-175

I had an interesting thing happen today that maybe someone here could explain to me why.

I tried to purchase a small parcel at 0.180c earlier today but commsec kept reducing my purchase price to 0.175c. The buy side was moderately stacked at 0.175, thus, due to my modest parcel I wasn't too worried in buying at a higher price. The reason Commsec kept rejecting it was because of an 'orderly trading' clause, a policy designed to prevent manipulation.

I found this odd as the only way to skip the 0.175 queue was to purchase at the next pip higher, being at 0.180c. In the end I was lucky and the order was executed at 0.175 but had someone not sold I would not have been able to get in.

Has anyone had this happen to them before?