110 Volts is nominal and may vary when measured by a voltmeter.  That said, power is supplied using sets of three separate parallel wires that you can see up on most power poles.  The very high voltage there is stepped down using a transformer to supply most houses and businesses with a usable lower voltage.  The voltage between any one of the three wires to ground in a house is 110 Volts for example to light a light bulb.  The voltage between any two wires is 220 Volts and is used for example to power a clothes dryer or kitchen range.  Houses do not use all three wires.  A machine shop may power a large motor by connecting all three wires (in a delta or Y configuration) to obtain 440 Volts.  Therefore the progression of 110, 220, and 440 Volts stems from the use of single, two and three-phase wiring circuits.  Electrical power is conducted cross-country at very high voltages using high tension lines strung in sets of three wires or phases which produces the multiple of 11 you mention.  Incidentally there may be an additional single wire above all the rest to arrest lightning strikes.
Why is the voltage ratinging always a multiple of 11 ?