Cite some sources? Because my state sure does not exclude basic groceries. When I look at my grocery receipt, it clearly states the tax percentage and is applied after everything is totaled up. If there is a state that does not follow this method, let me know.
Wherever you are (you don't say), I suspect your sales tax on groceries is more the exception than the rule. For just one example, Nevada doesn't tax groceries. If you're paying tax on a grocery-store purchase, it's for (1) non-food items (such as cleaning supplies) and/or (2) prepared, ready-to-eat foods (such as fried or roast chicken from the deli counter, vs. a box of frozen breaded chicken strips or a package of fresh chicken that needs to be cooked first and isn't taxed).