Chase uses a "provisional credit" system, but for small amounts, this credit often becomes permanent almost instantly.

Wells Fargo utilizes an automated system called the Wells Fargo Dispute Manager which is also similar.

Technically, it is Self-Insurance. Banks set aside a portion of their interchange revenue (the fees they charge merchants for every swipe) into a "Provision for Credit Losses." They use this pool of money to "buy" customer satisfaction for small errors rather than paying an employee $30/hour to investigate a $12 dispute.