To calculate sales tax you need to know following things:

First, how much is the base price of the item?

Second, you need to know what is the percentage on the dollar. (e.g. 5%, 6.5% etc).

Find out the sales tax in your area. Be sure you know the sales tax in your city, not just the state’s sales tax. The city you live in no doubt has a higher tax rate than the state.

For multiple items, simply add up the prices and multiply the subtotal by the one and the sales tax.

Sales tax rates and rules vary from state to state, city to city.