you would need to set up shipping rules in the eCart object on the shipping tab.
to set the shipping up so some items have shipping applied, you would need to create a new cart column, for the sake of example, lets call this column shippable. for the items that should be included in the shipping charge, set the value of this new column to 1 in the add to cart button, items that are not included in the shipping charge, should have that column set to 0 in the add to cart button.
on the shipping tab, you would set up a shipping charge for each total price break. the exact settings will depend on how you want the shipping applied.
If you provide more details on how you want shipping to work, I can give more specific instructions.
