The Rice University Neologisms Database

Used to express satisfaction at the [monetary] benefit(s) of an action. This word is onomatopoeic as it sounds like a cash register being opened, indicating the financial benefit of an action. The word has now been generalised to indicate any kind of benefit; it's often used after winning a game, an argument or after making a witty comment. Many people I asked agreed that the meaning was now becoming associated with achieving this benefit without having to work for it, or in some extreme cases, benefitting by a backhand or sly means.