What does "one per purchase" really mean on a coupon

I am sure everyone will run into this situation at some point so I thought I would address this.
You enter a store to buy your groceries and of course use coupons. When you go up to the cashier to purchase your 10 jars of spaghetti sauce with 10 coupons the cashier tells you that you can only use 1 coupon as it indicates "one per purchase" on the coupon.

Every retailer has their own rules for accepting coupons, however after addressing this question directly with a manufacturer, the response I received was that "one per purchase" means one per product purchased and not one per transaction.

If a coupon indicates "one per customer", "one per household" or "one per transaction" then this is in fact a restriction where you can only use one per transaction.

For some reason individuals interpret one per purchase as purchase meaning a transaction, when that is not the intent of the manufacturer. I have been told by cashiers that the store would not be reimbursed if they process more then one coupon per transaction, which is not true. The store will be reimbursed for the coupon, as well as a coupon processing fee, therefore the store is actually making money by accepting a coupon from you.

If you run into a cashier indicating that you are not able to use your coupon, simply ask to speak to a supervisor or manager and usually that resolves the problem. If that does not work, contact the stores Home Office and address this issue with them.