If you import from Square, but your item prices in square included the sales tax in the price (instead of adding sales tax as a separate line), how to now add sales tax?

Example: My bag of dog treats in Square was imported as a set item with a cost of $12.  This $12 was a flat rate that included sales tax.  I did not have Square calculate and add on the taxes.  So now Square cannot correctly calculate the taxes I collected (& paid).  How can I enter the total tax amounts i collected through Square so I can report accurately and get the proper tax deductions?