These programs fail on the floor, not in the paperwork. The businesses that run one well are the ones that settled these four things before day one.
The technology is the easy part: a terminal is configured once and then it does the same thing every time. What decides whether a cash discount program survives its first month is whether your prices are consistent everywhere, whether the signage is actually up, and whether the person at the register can explain it in one sentence without sounding defensive.
The usual failure is inconsistency — a website price that does not match the shelf, a promotion that forgot the program, a member of staff who applies it differently on a busy Friday. All three are avoidable, and each deserves more attention than the terminal setup.
Requirements differ by state and by card network rules, and they change. Confirm what applies to your business before launching, and review it periodically afterwards.