Tor usage will increase your traffic.
- When you're using Tor, you'll need to download information about all Tor relays (directory information). This list of all relays is downloaded when you start Tor Browser for the first time and updated on a regular basis. You won't have this kind of traffic on a non-Tor connection.
- Tor uses encryption for all internal connections. So each request from and to your computer is three times encrypted. Also this encryption step will add some bytes of overhead.
So there is some more data transmitted when you're using Tor. However I'd assume that this additional data are only a few percent of your overall traffic. So if you're browsing 3 to 4 websites more (like CNN, WaPo etc.) this will probably consume more traffic than the additional Tor traffic does.