I think that there is a difference between cheating and using your discretion.

I have worked in some 3rd world countries where you have to bribe people to get stuff done. I would NEVER bribe someone to win a contract but I have had to bribe to have electricity switched on, items delivered etc.

You can't put 'bribes' on an expense form and those people never give a receipt

In that case I will mention this to the accountants and ask them. If you are upfront about it, most will see sense but in some organisations perception is more important than money or even honesty.

A classic money saving perk is the helicopter from Nice to Monaco. It is cheaper for one person than a taxi for the same journey but the accountants don't like it. Even when you can prove that you have saved the company money. It is because they are stuck in a office and we are having a 'glamorous' life.