Billed per usage plan with carryover

Hey guys, I'm currently on a usage based plan but my app is only projected to use $1.70/month. Will I get billed for the $1.70 and the rest carried over, or will I get billed $5 per month regardless? If it's the latter, what's the plan I should sign up for if I want to be billed on the basis of resources used and the rest carried over until my credit runs out?

Or is there a minimum of $5/month billing either way?

It is going to be $5/month no matter what.
That $5 is up to $5 in usage. If you are only using $1.70, you will only be charged the monthly $5