You mean sum of total prices of all Opportunities? If yes, check this link http://blog.sonomapartners.com/2014/04/multicurrency-and-soql-in-salesforce.html
Donot forget to select best answer to make our efforts visible in the developer forum. Please mark this as solution by selecting it as best answer if this solves your problem, So that if anyone has this issue this post can help
If yes, check this link
http://blog.sonomapartners.com/2014/04/multicurrency-and-soql-in-salesforce.html
http://www.anthonyvictorio.com/salesforce/roll-up-summary-utility/
Donot forget to select best answer to make our efforts visible in the developer forum.
Please mark this as solution by selecting it as best answer if this solves your problem, So that if anyone has this issue this post can help