- Pay less for my drink and consider myself 10 pence up on the day (a major win on my part)?
- Pay less for my drink and donate the 10 pence to a good cause?
- Leave the machine with 10p in so that is causes the same conscience crisis for the next user of the machine?
In the end I opted for option 3. I kind of felt that my integrity was under threat. Options 1 and 2 would have me leaving with the extra money (and they wouldn't necessarily know it was going to a good cause). And it might be that somebody had just popped off to get extra change to finish paying.
And they say that us programmers obsess over small things....