Green’s Dictionary of Slang

an onomat. term indicating the noise of a metal object striking another and giving a sharp, bell-like note.

1960		H. Selby Jr ‘Tralala’ in Provincetown Rev. 3 82: The cash register kachanged and the smoke just hung and Fred came and joined the party.
1964		H. Selby Jr Last Exit to Brooklyn (1966) 80: The cash register kachanged and the smoke just hung and Fred came and joined the party.
2001		J. Stahl Plainclothes Naked (2002) 246: When he noticed the Polaroids, a sickening grin split his face ‘Ka-ching,’ Zank warbled.