So who are you sending the letter to? Whatever you do, don't send it to the advertised address for the job, because the minimum wage resume screening people just throw away the letter, and probably throw out your resume without looking at more than the first couple of lines anyway.

If you are sending it to the actual hiring manager, that has a chance of success. But if you are that invested in getting the job, why not go over to the office and deliver the letter in person, directly to the hiring manager? That's something that will help you sell yourself.

Good luck!