The Charge Credit Card checkbox being marked by default on new credit card sales transactions (e.g. Cash Sale, Payment and Customer Deposit) is an intended behavior. This checkbox is always checked on new transactions. It is unchecked when editing existing transactions. The Charge Credit Card checkbox does not do anything unless credit card information is entered. If no credit card information is entered, the checkbox will be ignored.
The ability to set the Charge Credit Card checkbox as unmarked by default is currently tracked under Enhancement 148021. Alternate solution is to manually unmark "Charge Credit Card" checkbox or just save it.