Can an employer make you stay after work if you are clocked out?

I've never come across anything quite like this before, but I'll give you a general response.  Federal wage and hour laws require employers to pay hourly employees for all "time worked."  Though there are thousands of cases dealing with what constitutes "time worked," it is usually defined as time when the employee is at the beck and call of the employer.  If your employer prevented you from leaving the business, I don't think it makes any difference whether you had clocked out or not.  If the employer required you to be present in the work area (the retail store), that would be considered "time worked."  The same would apply if the employer required you to work "off the clock."  Unless there was some reason you could not be allowed to leave the store after you clocked out (a security issue, or some other valid reason for preventing the public at large from entering or leaving the store, or you had clocked out after the employer instructed you to stay and help other employees,) I think the time spent in the store after you clocked out may well be "time worked" for which you would be entitled to be paid.