It's really nice that Indians now have their own currency symbol, but it is still to come up in common fonts available on our PC, so for the time being we need to use an additional font. Here's how you can install the font on your PC and use it.
First download the font Rupee Foradian.
Open C:\Windows\Fonts and copy the downloaded file there.
Windows 7 users please check here how to install the font.
Copy the downloaded font to /usr/share/fonts/truetype/ ; create the directory if required.
Now, start your favourite word processor software and use ` (back-tick) to use rupee symbol by selecting the newly installed font.
Enjoy using the new font.