Thanks for your answer.
However, the freight I need to add is not a percentage like a tax rate, but a fixed value. Selecting "On net total" evaluates the rate as a percentage though, thus returning the wrong result.
What I am looking for is a way to add a fixed value such as freight and have it calculated it over all items, so that the cost is included in the total price, but not shown in the printout. This is the common layout of quotation with price basis CIF that include freight and insurance.
For what its worth, I am still using ERPNext version 4.