In the past, my travel agent has booked a return ticket in the currency of the country originating the returning flight. For example, LA to Frankfurt paid in USD's, Frankfurt to LA paid in DM's. What I have never seen is LA to Frankfurt denominated in DM's.
Is the rule as follows:
Regardless of how many countries you visit, if your RTW ticket origninates in the US, you must pay the fare quoted by the airline in USD's?