Be candid with the interviewer about if you have or have had a Costco membership. If you currently shop at Costco, that's great! Be sure to mention how much you enjoy your membership and shopping at Costco. If you have had a Costco membership in the past, be sure to say that you have shopped at Costco, and you liked it! If you do not buy at Costco, that is okay too! Merely share that you do not currently shop at Costco, but you hear wonderful things about it all the time and look forward to being part of the team.
"When my kids were younger, and living in the house, my Costco membership is what saved me! Time wise and financially. Now that they are off to college, my visits are less frequent, but this is still my go-to place for holiday shopping."