Ethics Question

Let us say that you are getting on a bus. The fare meter has a little LED readout that tells you how much you have paid already toward the fare, so you can make sure you put the right amount in. (When you reach $1.50, it beeps, and the readout disappears.)

And let us say the meter already has ten cents on it. What is your obligation? Do you have to pay the full buck fifty, since that is the fare, or can you pay one forty and let the dime be a present from an earlier traveller who overpaid? I have, in the past, simply put two bucks in because I did not have change, and I would not be troubled to hear that the extra fifty cents was saved by someone else. The bus company is getting the right amount regardless. But I just don't know.

There is also an element in town that believes we should refuse to pay the new, higher, fare at all, out of concern for poor workers whose neighborhoods are already underserved, but I am going to leave that whole argument out of this.

What do you all think? Can you take the extra ten cents or not?