I appreciate what you've done so far. Let me help you generate a report that lists the total sales, including sales tax, over a specific period and then print it in QuickBooks Online (QBO).

Let's run the Sales by Customer Detail report wherein you can see your desired details on a specific report:

1. Sign in to your QBO account.
2. On the left navigation panel, select Reports.
3. Enter Sales by Customer Detail in the Search box, then click it.
4. Edit the Report Period to This-Month-to-date.
5. Click the small Settings icon on the report page to customize the report.
6. Click the Show More to expand the options.
7. Put a checkmark on the columns that shows total sales for one-month including sales tax.
   
   In a Classic View:
   
   
   
   In a Modern View:
   
   
   
   
8. Click Run Report.
9. Once done, click the Print icon beside the Email icon on the report page.
   
   In a Classic View:
   
   

In a Modern View:

Additionally, let's memorize this report so you can save its current customization for future needs: Memorize reports in QBO.

Moreover, if you want to send your memorized report through an email on a recurring schedule, use this article as a reference: Set schedule and email information for a memorized report.

Feel free to comment below if you need anything else regarding printing a report that lists the total sales for a month, including sales tax. Take care.