This is a preauthorization charge, and you will see this $1 charge fall off within a few hours (or days, depending on your bank or card issuer) and these funds will not post to your credit/debit card account.
Every card that is added to a CashorTrade account must be authorized with a $1 charge to confirm that the card is valid and belongs to the account holder. Each request to purchase is a separate potential "transaction" so each time a request is submitted a new $1 authorization is processed. Also, each payout requires a valid card on file, so before a payout can be initiated, a $1 authorization is processed to ensure the card on file is valid.