On the settings, tap Sales Tax.
Tap on Collect sales tax.
Fill in with a name and a rate (%).
There are two possibilities for Taxes:
Adding the rate to the final price. An example might be the service charge charged at restaurants.
That the rate is already included in the price, in this case, no value will be added, it is the case of Value Added Taxes.
If you choose to add the value to the price, you can allow exemption during the sale, just tap on this button to have the option.
Simply tap on the X of the Tax on the cart to remove it.
The Tax information will also appear on the receipt.