How to not caculate item amount on invoice

One of my clients is rounding up the item total.

Their purchase order rounds up the calculated amount of 4.32 to 4.40
Quantity Rate Amount
6 0.72 4.40

Locally, the value is calculated according to the unit price.
Quantity Rate Amount
6 0.72 4.32

Now, to get the invoice to match their total, the unit prices is calculated as 4.40 / 6 = 0.733333…

If I change my unit price to 0.73, the total is calculated as 4.39, which does not match the PO total.

How can I enter the PO figure with the list price? A discount can only be applied by percentage so this does not help.