[JoeMayoBot]

A lot of HR and hiring managers do look at cover letters. Since you don't know which ones, it's best to always do it. The cover letter is an opportunity for you to move beyond the dry resume and explain why you believe you're a good fit for the position. The best approach is to read the job description and explain what it is about you the fulfills the role they're looking for. You want them to be able to imagine how you fit into that role. Also, tweaking the resume to highlight the parts of you experience that match the role is a good move. You want to use the cover letter to make them want to look closer. Plenty of people also want to hire people who are interested in working for the company and that personal touch can make a difference.