I just checked both fares for this. V shows $278 plus $21.20 in tax and Q shows $358 plus $21.20 in tax on the initial purchase page. Now I have had this same trip and I do find once it is purchased, the fare and tax is listed differently, but comes out to exactly what you paid if you add the fare and tax together. I am not sure why it is listed differently on the receipt and confirmation once purchased other than some taxes are initially combined with the fare and then listed separately with the receipt.
ETA:
One of my most recent EWR-LAS-EWR tickets had a fare of $278.00 and $21.20 in tax for a total of $299.20 on the initial purchase page.
The receipt shows:
FARE INFORMATION
Fare Breakdown
Airfare:................................258.61 USD
U.S. Security Service Fee:..........5.00
Tax:......................................19.39
U.S. Flight Segment Tax:............7.20
U.S. Passenger Facility Charge:....9.00
Per Person Total:....................299.20 USD
eTicket Total:.......................299.20USD
The airfare you paid on this itinerary totals: 258.61 USD
The taxes you paid on this itinerary total: 40.59 USD