Only for a new cashier, really. It doesn't take long to understand what the customer is doing - once you've had a few "I can't make change for you because I'm out", it all makes sense and cashiers start to like the customers who minimise the change requirements.

I remember talking to someone who had clearly never worked in retail, complaining about their god-given right as a consumer to have change made for them trumping an open-air market vendor's right to have change for the rest of their sales for the day.