Try going into TextFX / TextFX Settings and check 'auto close XHTML tags'. This makes it work in plain HTML files too. You may need to install it if using a newer version of Notepad++
Click Plugins > Plugin Manager > Show Plugin Manager
On the "available" tab check the box by "TextFX Characters"
Click Install
Restart Notepad++
Enable the auto-close XHTM features as described above.
Best Answer
I've found a plugin that does that, Webedit and it's available in Notepad++'s Plugin Manager (Plugins > Plugin Manager > Show Plugin Manager).