I assume end shift vould be use for end of the day or maybe whoever in-charge of store have accounted the money and stock.
example; for cafe or fastfood chain, an food item may not be refund after the next day or a few days later. Even for electronic item, company from different country have different refund/return policy.
The other problen may face is cash drawer may not have enough physical cash to refund from the drawer.
it can also prevent thef from internal stuff who keep refunding previous day transaction.