The Raspberry Pi provides a 5V out pin at ~ 300 mA, so it should work, if the transistor works at 3.3V. Also, someone has tried it, and it worked. I just hope it's the same board.
FYI, It's ok to output at 3v3 volts to a 5v device if the device will still work, but don't read input from a 5v device or you might damage your Pi; the pins are wired directly to the Broadcom chip with no resistance.
