@brahmin,
As a business owner, I want to know that if I put you in contact with customers, you'll ensure that they leave with a better experience after working with you than they would have otherwise.
I would explictly state this in a form like this: "Mr Interviewer, you need to hire me for this job. I am the best candidate you'll interview for this position for the following reasons, [reason1], [reason2], [reason3] (make these quick, meaningful, honest 1-liners). My goal in working with your customers is to give them a better impression when they leave the store than when they first came in. This is important regardless of what they've bought or how much they've spent, if anything. Today's non-sale is tomorrow's future-customer, and as an employee of Macy's I will be an asset to the future success of this store's sales, and thusly the company itself."
I would then refer back to those 3 points in other questions in the interview.
Look at every question from the point of view of your employer, and all of your answers should serve to show how your employement can benefit THEM.