Let's start this story with the Massachusetts law that prohibits charging extra for credit card transactions
MASSACHUSETTS POSSESSES A "NO SURCHARGE RULE" FOR CONSUMER PURCHASES
"No seller...may impose a surcharge on a cardholder who elects to use a credit card in lieu of payment by cash, check or similar means."
Statute: Mass. Gen. Laws Ann. ch. 140D, § 28A(a)(2) (West)
Discounts for Cash Payments are allowed in Massachusetts
Discount offered to induce payment by cash, check or other means not involving a credit card not considered a finance charge if offered to all prospective buyers and disclosed clearly and conspicuously.
Statute: Mass. Gen. Laws Ann. ch. 140D, § 28A(b) (West)
Statutes cover: Credit cards only
Statute: (Mass. Gen. Laws Ann. ch. 140D, § 1 (West))
I drove over to the other town. I didn't have the excise tax bill with me because I had misplaced it. Since it can be easily looked up using my driver's license number, I wasn't concerned.
I found the payment kiosk. It turns out not to be owned and maintained by the Commonwealth, but rather by a private company (Kelley & Ryan Associates) that, it seems, has a contract to collect various payments (like excise tax or parking tickets) owed to the Commonwealth.
I initiated my transaction, following a system of prompts that began by offering me a selection for taxpayers who didn't have their bill right there with them.