Rather than be just a nuisance in their pocket, customer till receipts are very important pieces of paper and are a great form of proof of the existence of a very important contract between you, the retailer, and your customer.
It is illegal not to offer your customer a receipt for a transaction that has taken place. A till receipt can be used subsequently to prove that the actual transaction took place or can assist in the retention of a good customer relationship when a purchase requires to be returned to you for credit or replacement. Indeed, some retailers have trained their staff to make a feature of presenting customers their receipt with a sincere thank you.
So, having the correct paper roll permanently in stock is vital to the operation of your business.