In general, a merchant is not permitted to establish a minimum or maximum amount for a Visa transaction. However, exceptions apply in the U.S. and U.S. territories, such as Puerto Rico, U.S. Virgin Islands, and Guam. In those locations and only for credit cards, a merchant may require a minimum transaction amount of US $10 and government agencies and education merchants may establish any maximum transaction amount.
Ref: https://usa.visa.com/support/consumer/visa-rules.html
If you have a question about a Visa rule that is not addressed herein, please contact Visa at VisaRules@visa.com.