In my experience escalation to a manager is not necessary because usually the cashier will call a manager. In instances where a manager is not called but cashier refuses, usually it is better to walk away. However, if you know the management is friendly to your activity it can be worth it to ask for management. It can also be worth it to ask for management if there is nothing to lose (IE it's not just one rogue cashier but all/majority of cashiers refuse transactions).