As I posted previously, (see here) and I'll do it again as a public service:
Dealers are not allowed to charge fees to customers to participate in the CARS program. If you dealer tries to do so, above and beyond their standard fees, they are trying to cheat you.
The proof is here, from www.cars.gov/faq:
Can dealers charge me a fee for buying or leasing a vehicle under the CARS program?
While dealers can charge their normal types of fees, the CARS Act specifically prohibits dealers from charging a fee for purchasing or leasing a vehicle under the program.