tolerance of voltage in Japan

Hello. As far as I know,the household power in Japan is 100V. BUT WHAT IS THE TOLERANCE OF IT? Is the tolerance of +/-10% normal?
I hope somebody here can help me to clear up this question. I asked on many forums but I did not get a satisfying answer.
On this website http://en.wikipedia.org/wiki/Mains_electricity
I read some info about household power in different countries.
It is written there that all European countries use a supply that is within 10% of 230V.
The USA and Canada use 120V with a tolerance of -5% to +5% (i.e. from 114V to 126V).
But there is no such information about the Japanese household power. It's only written there that ''In Japan, the electrical power supply to households is at 100V.''
WHAT IS THE TOLERANCE OF THE JAPANESE HOUSEHOLD POWER? 100V +10%-10% or less???
Thank you in advance.

I used an appliance that is designed for US usage in Japan and no damage was done whatsoever. It was TV and worked just fine except frequency indeference.

So the voltage can range from 95V to 105V.

Adrian most of us have no clue about the actual voltage .All I know is that it is supposed to be around 100 volts and all the sold- in-the- USA equipment I bring and use in Japan works just fine. I am sure that the power also fluctuates in North America but have never ever worried about it.