I belive there are a number of ways to handle this topic.
But during my work with purchasing I have found 3 ways that are most common:
1. Using a pricelist converting from the currency in which the products are produed to currency in which they are sold/purchased. The exchange rate is then updated quarterly or yearly based on a mean value, found for example through
www.oanda.com.
2. Using financial instruments through banks hedging the currency risk. This cost money! But is a safe way for both parties, and makes it easy to only adjust currency fluctuation once a year. But offcourse, you loose money on this to the bank...
3. Not using any way at all to hedge the risk. This mean using no mean value and no hedging through banks. This could perhaps be the most common way. And just do the pricelist update once a year, by a "normal" pricenegotiation.
Hope this gives some ideas!