Shipping headache

Hi I’m working on a site for a friend and recently downloaded this plugin which seems really good however I’m a bit lost on shipping.
I can work out adding a overall added charge with the code shipping=”0.001 but what she would like to do is have the below added postage.
1 – 2 products $10
3 – 5 products $15
Over 6 products $20
Unlimited Products: $25
She only has 3 products on her site is this possible to set up?

Cheers

http://wordpress.org/plugins/wordpress-simple-paypal-shopping-cart/