Don't forget to input the customer's local sales tax (upper lefthand corner). Click to Lookup By Postal Code.
If a customer asks for something NOT listed below, simply use a comparably priced product.
It's ok to tell the customer: "It's gonna cost ABOUT (this much money). I can't give you an exact amount because I'm unsure about the sales tax. But it's going to be within a couple dollars."
(This is merely a tool meant to help calculate quickly)