The neutral conductor is a current carrying conductor and since it carries current and has resistance you will experience votage drop. The grounding conductor does not carry current (unless it is clearing a fault) and so it will NOT have voltage drop. You are comparing a conductor with voltage drop to a conductor that has no voltage drop, so you are actually reading the voltage drop. Five volts is a little on the high side, but not totally unreasonable for a fairly heavily loaded circuit. If this is a lightly loaded circuit, it may indicate a poor connection somewhere in the circuit. If this is the case, the first thing to check would be the receptacles. Make sure the connections are tight, especially if the receptacles are the type where the wire just sticks in the back and is held by a spring clamp.