@isotherm, I think you are looking at this incorrectly. Rather than trying to get this information from one of the tax reports, recognize the fact that non-taxable sales are not really involved with taxes collected, assessed, or payable at all. Yes, sales tax reports often ask for differentiation between total gross sales and non-taxable sales that are included. But tax authorities do that for two reasons: (1) so they can reconcile your report with other returns, such as income tax returns, and (2) simply as a way of seeing which portion of your sales is taxable (total minus non-taxable).
A better way to easily get the figures you need is to set up taxable and non-taxable income accounts. You can specify which tax codes apply to various accounts. For example, in my jurisdiction sales tax is collectable for remission to the government on most product sales, but only on a very few specific service sales. And different products or services might be taxed as different rates. So I might have taxable and non-taxable product income accounts and taxable and non-taxable service income accounts. In the chart of accounts, these could be grouped to get subtotals. The result is that you would get your desired income figures from the Profit and Loss Statement, not a tax report.