Well, before you get a job you have to apply for it. I would suggest at least getting the application and sending it in. Then, if you actually get the job you can decide if you want to take it or not.
Jobs are hard to find, so if you have opportunities I suggest you take them. You might find that cashiering is simpler than other social interactions because there's a template for it. You just say "Hi" and then you ring the stuff through, and then you say "your total will be ____." If you want you can make small talk about how much you like all the stuff they're buying, but there's no obligation to do that.
If you need a job, I would suggest applying to these places. I would also suggest looking around at other places where you would prefer to work, and applying to those too. Even if they don't say help wanted, you can always go in and ask if they're hiring, and give them your resume. That way you keep your options open and are more likely to get hired somewhere.
What kind of cashiering job are you thinking about anyway? Some will be more difficult than others, depending on if their is a high influx of customers, and whether your job consists of just ringing everything through, or if there are special things you have to do to complete purchases.