if i am not mistaken, if it was the specialist protecting his turf, even though he only posted 100s on the better bid, this wouldnt preclude him from buying more than 100s, i.e. someone comes in with 4600s sell in this example, he could take out the whole offer, .02 better.
chasinfla, i have software that allows someone to keep best bid/offer, in fact IB allows you to do so, i have seen this, but in this example the 100s would already have been best bid so i dont think it would be software.
easy way to find out though, next time place another bid .01 better and see what happens, if you get pennied again, maybe its software, or maybe someone takes out some of the offer if you get too close