I have the same problem and even if I stop nginx with /etc/init.d/nginx stop it is running on Debian Wheezy:

PID PPID %CPU VSZ WCHAN COMMAND
2709 1 0.0 127476 ep_pol nginx: worker process
2710 1 0.0 127716 ep_pol nginx: worker process
2711 1 0.0 127476 ep_pol nginx: worker process
2713 1 0.0 127444 ep_pol nginx: worker process
2714 1 0.0 125208 ep_pol nginx: cache manager process
3458 3218 0.0 6392 pipe_w egrep (nginx|PID)