Fees applied to transaction go to support the networks that run the coin/token. Currently, mining fees in Jaxx are dynamic - they are subject to go up or down based on the state of the network.
Price for BTC fees can be specified between three different fee options depending on whether your transaction is time-sensitive or not (as the lower fee may face a longer confirmation period) in Settings. (Menu>Settings> BTC mining fees).
This fee does not go to us; it goes to reward miners (thereby ensuring that the transaction is logged into the blockchain in a timely fashion) and support the network itself.
Note: ETH transactions that interact with a contract address will be more costly.
As newer coins are implemented, each coin is subjected to their own transaction fee that goes to their respected networks.