I'm designing the tables for a system that will eventually marketed in the US, {I'm in
Canada and the last time I did any work in the US, Sales Tax was only just starting to be introduced!]

I need some general
guidlines on Sales Tax calculations. I understand that tax rules can be quite complex, e.g. tax may
be waived for certain items for certain time periods based on the price. Right now, I'm just
concerned about the basic table design, the rules can be added later.

I allow for the fact that a customer or a transaction may be exempt from any tax.

1. Are there ever any more than 2 sales taxes?

2. Are sales taxes always a percentage, and never more than 3 decimal places?

3. Are sales taxes always based in the State, or can they vary within different Cities in the same state?

4. For a customer who could be an individual or a company, will the rate
always be the same?