Each store has their own policies as far as coupons are concerned. Some are very strict regarding their policies since they most likely have to answer to an umbrella company. Especially in nationwide chain stores, the policies for couponing are very specific and are expected to be adhered to by the cashiers in the checkout lanes. Their registers are preset with the limitations that the company has listed in their policies and in most cases cannot be over-ridden unless the umbrella company gives permission.
Those are the times when you really have to do your research for couponing. There are a lot of stores that will post their couponing policies online so you can print them out and add them to your coupon folder for reference. For other stores you may have to ask them for a copy of the policy.
When you present your coupons at checkout, some cashiers will balk at allowing them. If you have a copy of the coupon policy with you, you can politely and respectfully show the cashier the pertinent part of the policy that allows you to use those coupons. There are times when a cashier may not be aware of the full policy.
Remember to smile and thank that cashier for their patience in your use of your coupons. You will make a better impression on them than if you get upset, obnoxious or loud. There are times when some couponers are actually removed from the store without their purchases when they show a tendency toward violence. In the end it is usually because they did not research the policies of that particular store when it comes to the use of coupons. The other thing is that they get so worked up due to the enforcement of store policies that lose all respectable treatment of the cashier. The important thing is to know your rights in the use of your coupons and to follow the store policies in order to reap your savings.