For the small loads you're talking about there is no need, the IRF540 should be okay with a 5 volt gate drive. Mind you it seems a waste of the FETs capabilities but if that's what you have... no reason not to use it. If you can use a comparator as a buffer between the 5 volt logic to give the FET a 12 volt drive it will help, but the power dissipation is so low you're only talking the savings of a few milliwatts of power. If you go above currents of a about 100-200ma's you need to increase the gate voltage.