We like to invoice as whole figures so round up or down the total amount. Eg. I want to make the total job $300, so I adjust by either entering a separate line item with the additional amount or I'll use the discount with the dollar figure. It is very time consuming to do as it will make it 300.01 and no matter how you adjust it, once it saves it always shows an extra cent or less.

Having an option to put in the total and it automatically fills in either the mark up or discount would be great.