You can log into an active account with foxyproxy, do not have hotspot shield on at this time as it will take over your foxyproxy. TNT only logs your IP when you first log in and in some trades and auctions (I believe they log them in trades and auctions anyway, not completely sure.)
Just use different IP addresses and open 2-3 IE and go to tools>internet options>lan setting> Enter your proxy ip and port. Login to the first account. Deactivate the proxy and do the same for the rest.
You don't need to activate the proxies once you are already logged in, so enjoy. xD