Extra fee tax doesnt apply to total

Hi,

I am looking for a plugin which can apply a processing / administration fee based on minimum order in the cart.

For instance I want to apply 5￡ in administration fee if the total order is below 100￡.¨
I need to bee able to apply tax of the administration fee as well.

Do you guys know any plugins that can do this?

The page I need help with: [log in to see the link]