I've slapped the ask 3 or 4 times in the last two weeks and only once did it actually go off at the ask. A couple were more than a percent or so below.
you're correct. I've had several ask orders filled below my ask orders. it's not just GDVM they're doing it to, it's all stocks. I've got some stocks that trade for $1.00+, which means they trade in .01 increments. that means retail can place an ask order for $1.05 but not $1.049 which the order got filled at..
by the the way same rule applies to stocks like QDVM that trade for under a dollar the minimum price increment is .0001 not .00001..
News 
Market Data 
Discover 
