In Store -> Tax, you could configure your tax rates. To enable "Table Based Shipping", select "Table Based Tax" in the tax provider drop down list and click "Save" button.

Now you could start adding tax region. Click "Add Tax Region" button and you will be prompted a Tax Region Wizard. There are a few predefined tax region which you could load by clicking "Load Predefined Tax Region" Button. You could also define you own tax region. Enter a value for "Tax Region Name" such as New York, Washington etc. In "Tax Region Definitions" choose appropriate conditions that define the tax region. You could enter multiple conditions to define a tax region. These conditions are "AND" clause, meaning all the conditions must be met in order to qualify this tax region. For example, you could define "New York State" as two conditions: Country Equal US, State Equal NY. Note all the values to Country and State must be two-letter code. Click "Next" button when you are done with this step.

Next step is where you define the tax rate for the tax region. Note if the rate is 8.8%, please enter 0.088. When you finish click "Finish" button.