6mo. ago, I was terminated from my job due to excessive tardies. I was an otherwise incredibly hard worker with zero complaints, and I got along with all coworkers and superiors. How can I find out if my ex-employer will rehire me?

This is a deal breaker for companies. You were hired and given the guidelines of your job that you failed to honor. You were tardy over and over again.  You were tardy so often, their final remedy was to fire you because they couldn't count on you being on time for work.

Why would any company re-hire you when you were terminated for cause?

You will have to prove yourself worthy of showing up on time, ready to go, when you're supposed to be there. Not ten minutes late because the bus was late. Not fifteen minutes late because you were still eating breakfast. Not even five minutes late because you had to use the bathroom first.

If you have learned from your mistake, that's a good thing, but it's pretty doubtful that your old company would hire you back, given your track record.

Showing up on time for a job is one of the most basic fundamental requirements :) so no , you won't get another shot at that place of employment nor do you deserve one. But !! You can learn from this and show up 15 minutes early for your next job and that's SO AWESOME !