This seems like a very inefficient infrastructure to accomplish what you want to do.

By using Plaid to determine transactions, I assume you then do a once-a-month transaction that is the sum of all the round-ups? Or do you do a separate transaction every time someone does a transaction?

If you're doing a separate transaction, you're paying some ridiculous Stripe fees for the micro transactions.

I think the ideal solution would be to set up your own debit card. It's not significantly hard to get a branded debit card solution through Bancorp. Then you can control thins a lot more easily.

When a customer makes a $12.10 charge, you can actually charge them $13 and just keep the 0.90 on the backend and the processing fee is only paid once.