As a merchant, can I require a minimum transaction amount on credit and debit card transactions?

As the cost of processing credit cards increases it's not uncommon to walk into a business and see a sign that reads something similar to, "$10 Minimum on Credit Card Purchases".

While merchants that impose minimums are simply trying to avoid losing money on small credit card sales, card holders often find this practice very annoying. Aside from the customer always being right, in this case it's the card issuers such as VISA and MasterCard that have the final say.

Both VISA and MasterCard clearly forbid this practice as is outlined in excerpts from their respective documents below.

Merchant Rules Manual, Page 2-22
9.12.3 Minimum/Maximum Transaction Amount Prohibited
A merchant must not require, or post signs indicating that it requires, a minimum or maximum transaction amount to accept a valid MasterCard card.

Card Acceptance and Chargeback Management Guide for Visa Merchants
Dollar Minimums and Maximums – Page 10
Always honor valid Visa cards, in your acceptance category, regardless of the dollar amount of the purchase. Imposing minimum or maximum purchase amounts is a violation.

Both of these documents are available for download via the link at the end of this article.