How taxes work for each country?

[Maxtor]

My question is simple.

How taxes calculate percentage % for each country the customer is located?

For example if someone from US i think its 0% , but if someone from australia its 10% . 

is there a ready list for all country taxes? or its already loaded in IPS?

[opentype]

There is no universal list. It depends on what is legally required in your country. 
There can also be distinction between business-to-business sales and business-to-consumer sales and there is an additional condition within in the EU about VAT ID numbers. But again, all of that depends on your country. 

[Marc]

You would find what is being referred to above in Commerce->Payments->Settings->Tax Rates within your ACP (Admin CP). You can choose from either a single rate per country, Separate consumer and business rates, or European VAT rates where there is a differentiation between VAT-registered and none VAT-Registered companies