Hi there,
Welcome to the Community. QuickBooks is designed to help you manage your accounting with ease. I'll be happy to show you how to add a custom tax rate that you can use to enter a custom rate for the taxes in question.
In order to achieve the goal you've reached out about, I recommend adding a custom tax rate and here's how:
1. Go to Taxes.
2. Select Sales tax.
3. Select Manage sales tax.
4. Locate the sales tax agency you wish to add the new rate for, and select Add custom rate.
Going forward you can now use this custom tax rate for specific entries. Let me know if this info helps. I'll be one message away.