Told my supervisor that no matter what I could have said it would have been wrong in the customers eyes anyway, so I said very little at all. She agreed.
Sadly the customer was too uneducated to realize that machines have been rounding off for a long time. She then went off in a huff into the night and dismissed her outlandish claim.
To quote her “You are stealing 5 cents from everyone that way, that's illegal”
My supervisor thinks I am just calm and collected in tense situations, in reality, I just really don't care and don't have time for scumbag lower class pedants.