I agree with ~siantjudas. You're a new employee and you've already called in not too long ago. Show up and if they choose to send you home, then you can go home. Otherwise it can really look bad and may hurt you later on with this company.
I feel the need to start by saying it's your sickness, and you're the only one who knows what you can or can't do right now, and also that following anyone's advice is your choice and you can't blame people for what happens - just to say it. But here's what I would do if I were you.
Call in, tell them the situation and tell them that you're perfectly willing to work but only if they have something you can do without speaking. (If that's too much, ask a family member to call in for you and explain as much while you're there to sort things out.)
This shows them you're serious about your work, but given that you're a cashier- probably unable to do it. I've been in that position before, and it sucks But that's how I handled it and it worked out well.
Show up, and have them send you home (if they choose to). That way you tried to work and then they can see that you're actually really sick, and not that they just hired someone who isn't ever going to come in.