Yes, all fares displayed on Hopper are round trip and include all taxes and fees (no hidden charges here!)
Please note that your airline may charge additional fees for baggage, meals, seat selection, and other add-ons. Those optional fees are not included in the displayed fare in the Hopper app. If you would like to purchase one of these add-ons, you can do so directly with the airline after booking by going to the airline's website or app and managing your flight by entering your airline confirmation code.
Additionally, most airlines charge fees to cancel or change your booking.