How do you calculate a total including sales tax?

  Add the tax to the subtotal to calculate the total amount

Explanation:

Add the prices of items purchased to obtain a subtotal.

Multiply that subtotal by the tax rate to determine the tax.

Add the tax to the subtotal to calculate the total amount.

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Example

Purchases total 6.95. The tax rate is 8.2%.

The tax due is ...

  0.082 × 6.95 = 0.5699       rounds to 0.57.

The total amount due is ...

  6.95 +0.57 = 7.52

Comment on percent

The % (percent symbol) is a fancy shorthand way to write /100. That is, a tax rate of 8.2% means you multiply the pre-tax amount by 8.2/100 = 0.082.