You can define Pricing Rules for your exports to Amazon, these rules apply to prices including all taxes.
You can define a global pricing rule for all your products in Platform tab, or by profile.
Pricing rules are ranges, for each range you can set a value or a percentage.
Here is an example:
In this example, all the prices of your products between 0 and 100 euros will be increased by 5% and then from 101 to 500 by 3%, and for 501 euros and more by 1%.