If you can belive Bittrex FAQ there are no deposit fees:

Deposits - There are no fees for deposits. Please be aware that some coins require us to move your funds to another address before we credit them. This means the coins network will charge you the normal transaction fee for this send. This is not something we can avoid.

source: https://support.bittrex.com/hc/en-us/articles/115000199651-What-fees-does-Bittrex-charge-