I would agree with a lot of what is being said here.
There is a PDF somewhere that goes over various studies. It depends on what you are selling on whether to do $19.95 or $17, for example.. or $47 or $49.95.
But, in my opinion, look at what the competition is pricing their products at, and beat it. And end with a 7 or "9.95" and you should be good to go.
Or, become a "premium vendor" and offer a higher price with a lot better service or much higher quality if you believe there's a market for it.