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?

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. 

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