It seems to me that these two words have the same meaning. The dictionary doesn't help much, it gives them as synonyms. Although the meaning of "сейчас" is more general and can refer to past events:
"Мы сейчас смотрели фильм" - We have just seen a movie,
in cases when they both refer to present events, they seem to mean the same:
Я теперь работаю в Microsoft.
Я сейчас работаю в Microsoft.
Is there any difference between сейчас and теперь in case when they refer to the present?