^^^In Canada, there's a straight 10% duty on these items, plus PST and GST (provincial sales tax and goods & services tax), and then whatever broker fee is being imposed by the carrier. I noticed that on a couple of my DHL items, they were charging 18% duty, which I'm in the process of investigating. Sometimes duties aren't imposed - when I get certain items from the U.S., they just charge PST and GST. The border officer said that the rules and regs are completely out of control and showed us a yellow pages-sized book that contained the info.
He said it's insane, and that it differs depending on the item and not only the shipping origin, but the country of origin of the item itself. An Hermes scarf, made in France, was charged at a higher rate several months ago, despite its U.S. shipping origin. I don't know if that helps, since you're in the U.S., but it might give an idea of how they work it.