i kinda have fun reporting people, but i usually ask the owner/ manager if they know they aren't supposed to do that. a lot see others doing it, so do so themselves. because they are charged a flat rate + a percentage so the smaller the purchase, the more the flat rate charge looks. i also reversed mc/visa. it looks like visa you report to your credit card company but mastercard will take care of it for you. not sure if canada is different, i'd think not. also i'm also pretty sure the same rules go for non-profits. i did some research about 4 months ago as an art co-op my wife was in wanted to have a minimum purchase and she had me do some research. there's a lot on google if you hit upon the right keywords.
http://usa.visa.com/about_visa/ask_visa/index.html?it=search#anchor_4Visa merchants are not permitted to establish minimum transaction amounts, even on sale items. They also are not permitted to charge you a fee when you want to use your Visa card.
If you run into a problem like this with a merchant, please notify the financial institution that issued you your Visa card. These institutions have access to the appropriate Visa rules and regulations and can help you document and file your complaint. You'll find their address and/or telephone number on your Visa statement. Their telephone number may also appear on the back of the card itself.
from
https://www.mastercard.com/contactus/contactus_mv.htmlReport a merchant violation
In order to make a MasterCard purchase, the merchant/retailer required a minimum or maximum amount.