From what I understand tax isn't taken out by google if you are not associated to any US Company or have no US Tax paying staff (Anyone who provides content for your site and is in receipt of any payment for providing the content), then you wouldn't have tax taken out.
However, that doesn't mean that you would not have to pay tax or be liable to pay tax in your country. It will vary from country to country depending on earnings and tax threshold.
It is highly advisable to set aside the emergency tax rate ( ie in uk emergency tax rate is 25% or so of gross - that is not exact but it is a nice easy amount to set aside).
This means if you have already set the money aside then when the tax man comes knocking, you will have no problem paying... so keep your receipts of deposits - basically you would be treated on a self-employed or contractor tax basis and as such other things may be required as well... especially if you are already working in a job you would then have your money counted as a 2nd income and a different tax rate would be applied to that.
I used to work in a tax environment and there is only one sure thing that will happen... if you dont make provisions for paying your tax and when the taxman catches up to you, then you are left with a lot of headaches.
This can happen even for a small amount as they can impose legal process costs etc so have the money set aside and find out exactly what the tax implications are for your area. Google is not accountable for that - but can provide tax authorities anywhere in the world a complete history of documented payments if required... this would mean paying a fine to the taxman to cover the expense basically
Hope that helped you out - I am no longer involved with tax matters at all, although very interesting, it just wasn't what I enjoyed
