Is it okay to ask for another interview before accepting a job?

I'm not sold completely on a job yet. During the interview process I felt that all my questions were not answered or I just have more questions. I haven't been offered the job but if we progress... I wanna know if it's okay to ask for like another interview so I can ask more questions to understand the job better. Is that frowned upon? My questions are job related and then I have questions about benefits and such. When is the timing best to ask these?