Converting to one currency within report

Converting to one currency within report

Hello - my business has sales in various currencies - ZAR, GBP, EURO, CAD and USD to name a few.  I have created a report that shows monthly sales by rep.  It's made up deals
in all of these currencies.  I would like each deal to be converted to USD.  Is there a way to do this using a formula column?  If so, i'd love some step by step guidance.  Thank you!