A Matter of Cents

You know, we don't usually deal with IMPORTANT stuff on a regular basis. So why is it the most mundane day-to-day stuff that drives one (OK, me) a little nuts?

The sales tax law is fairly arcane in New York State. It reads, in only small part:

Tax Law § 1115. Exemptions from sales and use taxes.
(a) Receipts from the following shall be exempt from the tax on retail sales imposed under subdivision (a) of section eleven hundred five and the compensating use tax imposed under section eleven hundred ten:
(1) Food, food products, beverages, dietary foods and health supplements, sold for human consumption but not including (i) candy and confectionery, (ii) fruit drinks which contain less than seventy percent of natural fruit juice...
[Emphasis mine]

I go to the corner store to buy a bottle of juice. The proprietor carefully peruses the bottle, notes that it's 100% juice and correctly rings up the sale on the non-taxable key. I mention how strange the sales tax law is, that if the beverage were less than 70% juice, it'd be taxable. The proprietor scowls, "No, if it were 99% juice, it'd be taxable."

So this is is my issue: should I go print out the law (actually, I already have, and have highlighted it to boot) to show the proprietor, or should I let it go?
Certainly, I was mildly peeved with his dismissive tone, but it's also the case that he's charging tax on some products that just aren't taxable. Then again, how many beverages ARE there out there that have between 70% and 99% juice, anyway?
The tax in the state between the state plus the local is about 8%, so on a $1.50 drink, it's only 12 cents.
Is it the "principle of the thing" or is it just ego?

Another example of the same thing: I bought one donut from the Dunkin' Donuts in the 20 Mall a couple weeks, generally 79 cents when I buy it elsewhere, but 85 cents there. I saw her ring in 79 cents, but it must have been on the taxable button, the button one would use for prepared foods to be consumed. Restaurant food is taxable, but a dozen donuts (which one would HOPE would not be downed in one sitting) is not. I seldom go to that mall, so I'm not likely to go complain over six cents, but still...

Veering off topic somewhat: I had this friend from Manhattan. For some reason, I mentioned that she lived in New York County. She became indignant. "No, I don't, I live in Manhattan County." I agreed that she lived in Manhattan borough. "And I live there," she scolded. "I ought to know!" Yes, she should, but she didn't. I let it go.