I think that outfit would work, wear black shoes

Never interviewed with retail sales, but I think what's really important to show is that you have a great attitude towards customer service. That you are confident, likable, great people skills. 

Also, this page might help: http://www.ehow.com/how_5594056_improve-retail-sales-skills.html

As are some of the skills listed on this page: http://www.careerbuilder.com/Article/CB-678-Cover-Letters-Resumes-Basic-Skills-Resume/ - hardworking, attention to detail, flexible etc

Good luck!