Drink some chamomile tea before, helps with relaxation, and please make sure to disclose your stutter at the very beginning. Frame your stutter as a tool that has helped you gain valuable and attractive qualities that any future employer would want in his crew. You can bring up situations from the past, that deal with your stutter, that highlight good qualities that can transfer over into a retail job. Don’t be afraid to ask THEM questions as well. Always remember, job interviews are chances for BOTH parties to see if it’ll be a good fit. Good luck!