...there was a court case a while back that required businesses to accept "coin of the realm". The case was that someone insisted that a product be paid for by a credit card. The potential buyer refused, and cited an FTC(?) rule stating that if a purchaser offers to pay for a good or service with legal tender (read: cash) and the seller refused, the purchaser can assume that the seller is offering that good/service for free. So he took it and walked out of the store. The seller had the "purchaser" arrested, it went to court, and the "purchaser" won.
I see a test case coming for the first person whizzing through your Tejano-IPass-equivalent waving a dollar bill for the requisite closed-circuit camera to see.
(Hell, if I were better fixed, I'd do it myself!)