Actually, the Turnpike does. The resident discounts on the harbor tunnels now require Fast Lane (and have since it was introduced, IIRC), and the two toll barriers on the Extension give a 25-cent discount for Fast Lane customers.
I believe it's actually written such that you don't have to use Fast Lane, but you're unlikely to have saved all those receipts in any other form.
Garrett A. Wollman | As the Constitution endures, persons in every email@example.com | generation can invoke its principles in their own Opinions not those | search for greater freedom. of MIT or CSAIL. | - A. Kennedy, Lawrence v. Texas, 539 U.S. ___ (2003)