Have you tried logging back into your account and printing a receipt? It's been a while now since I've done a Priceline, actually, but there was always a receipt that was slightly different from the booking confirmation screen.

Now, I've never really seen them put the details on it, though. Priceline is coy about the tax paid because they don't want you to know what the real price of the hotel room was vs what Priceline charged you for it, and they don't want you to know how much of the "taxes and fees" was their fee vs how much was actually the tax. There was some kind of controversy over this a while back, but I'm not sure it resulted in any significant changes.