Let’s say your taxi bill comes to 200 RS and you only have 500 RS bills, or even worse 2000 RS bills (which is a very typical scenario).
The taxi driver will, without any exceptions, claim not to have any change.
Your only option is to go somewhere to change, which will hardly happen. Most probably you will give the driver the 500 note
First mention to go somewhere to change. Then offer that he can give you just 200 back on the 500 note, instead of the correct 300. Now the driver surprisingly find the change somewhere in the wallet or car.
He earns a 100 extra, you rescue 200. Win – less loose.
Need to change a 2000 RS bill?
Do the same as above but (if needed) offer to accept 200 RS less than what would be the correct change. The driver will find change even for the 2000 RS note. He win 200 and you have a lot of change so you can reduce the number of times you have to do the trick the next hours.
This obviously isn’t a good investment model but it reduces the no-exchange-loss.
However, we are still the losers, since the taxi driver always wins.