Why are you interested in our organization?

For most stores:

'I shop at [Store/ etc] quite frequently and all the employees I've seen here seem to really enjoy doing their jobs. The work environment is friendly. Problems are handled thoroughly and courteously on both sides. I find it to be a company I'd love to associate myself with."

For a specialty store, you are going to want to mention the products they sell and the methods they use in a positive way.