Associate a product with tax within the Product Details section

Associate a product with tax within the Product Details section

I am finding that even though we are checking an item as "not taxable" it is still calculating tax for the entire subtotal.  Since it seems there is rarely a way to fix something "at this time" I am trying to figure out how to make each item/product associate with a tax amount (there is a column in product details for itemized "tax amount") and then I just would not associate the non-taxable items to any tax, so they wouldn't calculate.  Has anyone else figured out a way to NOT have specific items not associated with tax?  (I swear it used to work!)