Hi emily102,
Thanks for reaching out to us here. QuickBooks offers a versatile tax module that simplifies the way you manage your taxes. I'll be happy to share info and steer you in the right direction.
In order for the program to calculate the taxes correctly, it's important to make sure you've set up the taxes appropriately. I encourage you to check out this article here that shows you how to set up sales tax. Once you've set up the taxes, they can be added to your invoices and receipts using the default QuickBooks tax breakdown format.
You're welcome to ask other questions. I'm here to steer you in the right direction.