You could set up a current liability account for tips collected.  It will basically be a clearing account for the tips.  When you pay out the tips from your cash drawer record it as a debit to the tip liability account.  When you received the credit card payments record the tips as a credit in the tip liability account.  If the account has a balance in it, it means that either you haven't paid out all the tips or your haven't collected from the credit cards yet.  

The tips don't affect your profit or loss, but you need to track them for each employee to report properly to the IRS.