Have you ever been sitting at dinner adding up all the food and drinks your family just had, trying to figure out what the final price would be with tax? The formula is simple and requires basic math skills, and there is even an online calculator to help. The real complication is in knowing which sales percentage to use. Every state has a different sales tax, and different items (food, tobacco, etc.) are taxed at different levels.
Figure out the total sales price. For this example, let's use $19.99.
Figure out the tax percentage on whatever is being purchased. The Sales Tax Clearinghouse website will let you search for tax rates by city and state. Let's pretend this is New York City, where the total sales tax is 8.875 percent.
Multiply the total sales price by the sales tax percentage; 8.875 percent translates to 0.08875. This number multiplied by 19.99 gives us a total of $1.77 (rounded up).
Adding the total tax to the original sales price will give you the total price of a purchase, in this case $21.76.