In the context of the state and local tax deduction when you're itemizing deductions, this is the sum of your state sales tax rate and your local tax rate.
For example, if your state sales tax rate is 7.25%, and your local (city) tax rate is 1%, you'd enter 8.25%.
If you'll enter your city, state and "total sales tax rate" into any search engine, you can find your relevant rate quickly.