Just to pick nits - you'd be reducing the number of transactions, but not necessarily the bandwidth requirements. You still are reloading all of the content for those 10 nodes every time you submit votes. Asynchronous requests would only send the vote information & (user id, node id, vote type) and receive confirmation information (current reputation tally for node).

Adding up all that data you still have less bandwith required in total.

AJAX excels in reducing bandwidth when you do things like this - decoupling functionality from content and only sending page updates rather than the entire page. Yes, you might increase the number of transactions, but you are making their function more granular and thus simpler to process with less overall generated network traffic.