You can add 1 or 2 sales taxes to your quotes and invoices.
You can assign or modify the sales tax percentages.
Go to Setup -> System Values
Once there, go to Tax 1 or Tax 2 tab:
a) To delete a tax percentage from your list click on the trash can
b) To modify a tax percentage click directly into the value
c) To add a new tax value click on "+" symbol
d) To set a default tax value mark it from the default column.
TIP: When selecting a default value, this will be added to all the quotes.