I think it would be good to have on the lead screen like a floating button like the CRM Task Button. A quick pop up if you need to do a fast calculation while entering an order. It would make you not have to click on a software calculator on your computer but keep it totally within IO..
Just a thought.. I find myself many times a day using a calculator to adjust pricing or work up a percentage discount or deal, calculate a tip, or deposit, etc.
Just a thought.