Yes, you can analyze transactions for roundups from a linked credit card. All you have to do is add a checking account to fund those roundups.
Let’s say you add your Chase checking account to your ChangEd App, and later link your American Express credit card for us to analyze your spending and round up transactions.
In this case, we would round up transactions made on your AMEX and make ChangEd transfers from your Chase checking account. We don't want to be adding to your debt, right?