Good observation, Nholzmann01. Let me share how it works in QuickBooks Online.

When you create customers, you have the option to exempt them from sales tax. It's different from the project, though. It may be under the tax-exempt customer. However, you're unable to edit and exempt the project itself. That's why the sales tax is still calculated.

You'll have to uncheck the TAX column manually as a workaround. This way, sales tax will not calculate. 

I'll include this article to help you learn more about sales tax in QuickBooks Online: Use automated sales tax on an invoice or sales receipt.

If you have additional questions, don't hesitate to get back to this thread. We'll reply as soon as we can. Keep safe!