No, there should not be a tax on currency trading, because that will hurt economies. Nations need to be able to do business with each other. If they cannot trade currencies, because of large taxes, that will hurt business agreements and make the economy contract. It is better to allow businesses to work openly.
I don't think people should have to pay yet another tax on something that isn't even in whatever country an individual may be from.If people need to exchange currency I think that shouldn't be taxed because if an individual wants or has to go to another country you will more then likely need to exchange currency so why should there be a need to tax that money i believe its just another way to gain money from those who work hard and or already being taxed.