I found a topic about this exact thing for the SQL Reporting Services Nevron charts:

http://forum.nevron.com/shwmessage.aspx?forumid=4&messageid=3315

I have data labels that contain dollar values which have a tendency to overlap. How can I rotate the labels to 90 degrees so that they don't block each other out? I see no orientation option in the "text style" field in the data labels tab.