Your rounding cards are the cards that you wish to have your change rounded up from. For example, if you make a purchase using one of your Rounding Cards for $5.64, then $0.36 will be added to your total donation amount for the month.
In order to connect your card, you will need to login to your Bank/Financial Institution to verify the card. Your banking information is tokenized and protected via Plaid's partnership with your bank. PWI never sees or stores this information.