> I am not aware of any us state that charges sales tax on staple food items. Also I feel sorry for anyone that lives in a place with 10% sales tax that is crazy high
Most major US cities are at 8-9%. Many smaller cities (and St Louis) are more than 10. Cumulatively it's a lot of people afflicted.
Also, I'm with you on staples not being taxed, but that's part of the problem with the tax being added later instead of precomputed into the total; if you're shopping at a general purpose store (the Walmart in Mt View AR has been an offender for awhile, but I rarely find perfectly correct tax calculations on receipts for all but the simplest of purchases at any store) and buy a mix of staples and clothes and whatever, very frequently you'll find that staples were taxed, and if you weren't tracking things closely you'll have missed where the extra few dollars went. You don't know till the register what the price will be and can't easily plan ahead.
Another related problem, especially in the poorer parts of the country, the cheapest calories you can buy, especially if you're working too many jobs to have time to cook, are often excluded from such tax exclusions to discourage unhealthy eating habits (note also how obesity negatively correlates strongly with income). If you go into it with a vague notion of food not being taxed you can get surprised with 10% sales tax, a 5% junk food tax, and often a 10-50 cent (on cheap food a non-negligible percentage) plastic use tax or some other crap.
And so on. The problems stemming from not knowing what you'll pay are common and real, and they disproportionately hit people who can least afford it.