I find that prices are more consistent when there aren't a bunch of items of the same type/quantity ending together. By that I mean that one or two of them will often slip through at a significantly lower price. With that in mind, when I post items I always make sure that there aren't a bunch of other items also at that same time.
Also, I have found that by placing my max bid from the start I reduce the chance for the last 5 min to recycle. The longer an item sits in the last 5 min, the more it will cost. I was buying a lot of ointments the other day when prices were low and found that if an item went above my max bid (so that it recirculated the 5 min) that it would end at a significantly higher price than the ones that did not. Sometimes as much as 2x a matching item ending at the same time.