I've been using this paypal fee calculator to figure out paypal fees. http://www.rolbe.com/paypal.htm
with GingerandHoney's help (thank you!) I figured out that it's off by five cents! I know that five cents isn't a lot of money, but I hate the idea of overcharging people by any amount. I will find a different calculator to use and actually check to see that it's accurate from now on.