However unless your SP is lover than 10000+ that would be pennies anyway, so mostly I just vote for people and content I like to have around, sort of trying to create a good environment for me.
Even if my upvote is worth less than $0.01 , it helps to make a post to be on Active page that gives more chance for it to be noticed . Comments are working the same way.
Besides your upvote encrease Reputation of account you upvote.There is a good article about curator rewards https://steemit.com/steem-help/@liberosist/mind-your-votes-an-investigation-and-guide-to-maximizing-your-curation-rewards
That was a seriously good guide