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The U.S. has no national tax on goods or services. Most states and some counties and municipalities have sales and/or use taxes on goods and services, with rates varying from state to state, between municipalities, and even with regions of a state. Treatment of services, and specific classes of goods - in particular, cars and food items, vary between venues. As a practical matter, you need a subscription to a data service to keep this up to date.
It's unclear just what your purpose is, though. Is this an internal billing program for your own business? Or is it a script to be sold to others?
Assuming you are in another country, I don't believe there would be any sales tax, as you aren't within the jurisdiction of the taxing authority. Many states, however, have reciprocal agreements with other states, so that tax is often due on goods sold by a company located in one state to a resident of another.