What are the advantages and disadvantages of an "open gradebook" policy?
Case study: The biggest upwards bump I ever got in student evaluations was when I started making all course and assignment grades available on the school's digital learning management system (accessible 24/7 online by student login). Previously I'd noticed that my lowest score was in the category of "Instructor keeps me informed as to how I'm doing", and using the LMS to make all grades visible immediately fixed that.

I would argue that more transparency is always better in cases like this. It serves to clarify policies to the students, allows both sides to double-check, and reduce student anxiety (all of which are good things to model). My opinion is that this is the direction that reduces student inquiries about grades. 

I have had some colleagues who argued the same "Don't release grades so students can't argue about them", and I've never understood that. The whole situation feels more tense and high-stakes. The only downside I can think of is that open grading gives somewhat less flexibility to the instructor, in that it forces them to be honest and not goose scores in either direction for extraneous reasons.