am of d7000. faced the same problem. you can use the AF fine tune to tune the focus. the back focus is a known issue. look back at the user manual on the AF fine tune

you can read more :
http://photographylife.com/how-to-calibrate-lenses

hmm i'm not too sure cause each body back focus is different. after i set my af tune, i zoom in , zoom out.. the focus is still sharp, no problem.. i think you need to play around with the af tune until you get the best tuning.

try the diy focus chart.
http://www.dphotojournal.com/focus-test-chart.pdf