No, almost certainly not. There has to be a justification for excluding the public from a council meeting. Valid justifications would be, for example, to avoid breaching an obligation of confidentiality, to avoid revealing information about an ongoing legal dispute, to avoid giving private information about employees.
It's hard to see how deliberation over the precept could possibly fall into this kind of consideration. It is a fundamental duty of a council to decide on its precept, and the decision and the reasons for it should normally be made in public.