Is it possible to find the top % of an Amazon category using the Product Advertising API?

I want to take the top 5% of an Amazon category using their API.

Basically, it would return the ASINs/UPCs of the most popular (top 5%) items.

How could this possibly be done?

From my knowledge, you have to specify a query (which I'm guessing can't be null) even when searching in a category.