If you are shopping and come across an item that states "sales tax included," you can figure how much of the price goes toward the sales tax and the actual price of the item. If you know the sales tax percentage, you can easily "back out the tax" by a simple calculation on your pocket calculator.
Enter the total amount due on your calculator. For example, if the total is $13.65, enter that amount and hit the "Divide" key on your calculator.
Enter 1 and the sales tax percentage. For example, if the sales tax is 5 percent, enter 1.05 and hit the "Equals" key.
Read the result, which is the actual price of the item. To complete the example, an item selling for $13.65 tax included, with a 5 percent sales tax, actually costs $13, with 65 cents going for sales tax.