I try not look at USD anymore. I look at satoshis, since the minimum payout is 0.001 satoshis no matter how many dollars at the time it's worth. Also, lately I have been using Nicehash to get up to the minimum .005 satoshis to buy hashing power, and using that hashing power to mine XMR since I have no AMD cards. I'm up to about 50% of a payout on Nanopool, so I have to keep going.
That's a smart idea!