Each item within your inventory will have an option to assign a tax rate. Luckily, unless you’ve changed the setting, the item will have the “default tax rate” selected. This means that you can simply set a defaulted tax rate for your items.
To do this, you will want to select the Setup app. You should see a tab for Taxes. Here, you will select the default tax rate, and set an amount. If you would like to have a separate tax rate for some menu items such as alcohol, you can create an additional rate. When creating an alcohol item, you will select the proper tax rate.