Consider the display of hotel prices... Per night without tax, Per night with tax, and Per trip (all nights and taxes added together)
Generally there is a marginal popular winner, that varies by country. However, without fail once a decisions is made the next person I ask or test with seems to want it the other way. To the point where I've considered suggesting letting the user adjust the setting. But I know this will end poorly.
What research would you recommend to help get to a more definitive answer? Or is it a situation where we are just going to have to live with upsetting some users?