Depending on the actual load current there are several "Better" methods for an Accurate 5V reference. I think this is where your Education will truly begin. This is NOT a low power design so I might recommend a TIL 431 which is an "Adjustable zener diode, it takes a pot and a resistor to make a Stable any voltage reference from 1.25 to 30+ volts and is better as a reference than a 7805. On the subject of 7805's I personally remove them any time I can use a switcher instead, If noise is an issue several caps and a resistor or small coil w\ill deal with that Easily. (I do own an analog scope a Tektronics 2213) and finding and dealing with noise isn't a big deal for me. The TIL 431 is the simplest answer to your reference issues, simple because it is a variable shunt regulator and although there is always the pink noise issues with Zeners this device has it's Zener buried well enough that any generated noise can be dealt with with a .1uF and a 10uF cap.
Doc