We need a handling table based on item quantity

Currently, a handling table can be set-up based on weight or on the total cost of an order.  We need it to have a handling table based on the quantity of items being ordered.  So we could set-up a table like this....

Number of items ..... Handling charge Per item
1 ................................... $2.00
2 ................................... $.10
20 ................................. $.05

There is another difference from the weight based handling table and that is that it would use ALL of the quantities and not just the range that matches the quantity being ordered.  So, in the above example ...an order of 2 units would get a handling fee of $2.10 and not just a handling fee of $.20.  It charges $2 for the first item and $.10 for each additional item (2 though 19) and $.05 each for items 20+.