How to Calculate Sales Tax Manually?

Find out what the percentage is for sales tax in your area. Multiply that number by the number of dollars you have spent. That will be the amount in cents that you need to add to your cost. For example, if you are in a 6% area and have spent 10 dollars, you would calculate 10 times 6 is 60. 60 cents is your tax, so you would add that to the amount you have spent, $10 plus 60 cents is 10.60