There will be times that you just know you might run into an issue. Did Tylenol go on sale for $1.99 and you just happen to have 200 coupons for $1 off that can be doubled? There just might be a limit to how many of the same item can purchased in one transaction. There are actually several stores that have a doubling policy that only applies to 2-10 items per transaction. Most stores do not have a per person policy though.
Another instance that can make you divide out transactions are those store promotions for a $10 off a $50 purchase. Remember that when you use coupons, they are considered a form of payment, so the $50 is the before coupon and tax price. If you are buying $200 retail worth of stuff, you will miss out on $30 if you ring it all together.
So, the way you work this is to plan out how many items need to be on each transaction. Have a plan before you reach the belt and tell the cashier what you are doing so you don’t end up with a mess.