Until now. It turns out the valid cheat code is '00000'. It seems this is to enable international customers and non-US cards. Apparently using this code with a US credit card doesn't work since of course your magnetic strip contains your zip code.
Is this common published knowledge? If yes, then I just learned it anew. If not, I hope this helps someone. Does anyone know if this is just a workaround or intended to be an undocumented feature?