What Is Sales Tax?
Sales tax is a percentage of a purchase price added on top at checkout, set by state and local governments and varying widely by location. To find the total price, multiply the pre-tax price by (1 + the tax rate as a decimal).
Example
A $50 purchase with an 8% sales tax costs $50 × (1 + 0.08) = $50 × 1.08 = $54, meaning $4 in tax.