USPS limits $20 'per occasion' and not more than $50 per calendar year.
Many departments will just outright say nothing at all, or impose very strict requirements on reporting, or displaying/sharing publicly.
The way it’s worded sounds like it can be a gift card, just not one that could be exchanged directly for cash.
(PDF) https://www.irs.gov/pub/irs-tege/p_4090_fed_0305_text.pdf