For clarity, I am what religious people call an atheist. Personally I reject that word because I dint see why we need words to describe people who don't believe in thing that doesn't have any basis in reality. For example, there is no word for people who don't believe in fairies, ghosts, or such like. I find the word "atheist" patronizing and insulting. That said...

If faith is a conscious choice, yes it can be rational.

So, if a person says; "yes that book is full of stuff I want to follow because they believe that it will be a good guiding light for me and I chose to believe that the supernatural being the book insists is real such that it helps to keep me following the rules in the book out of the fear that the super being will judge me", then to me it makes rational sense. Its a rational choice. They do know that in reality is is not real, but they chose to live that way. The choose to engage in faith. Very useful for example for recovering addicts, or people who have faced some trauma.

What I will never understand is people who literally believe a given god and there for religion is absolutely true or real. Worse still is when children are brain washed from birth to believe in such gods.

So, if its a conscious informed choice to have faith, then yes, it can be perfectly rational.

I am reminded of a conversation between the Arch Bishop Of Canterbury and Ricky Gervais. After not long, the Arch Bishop essentially conceded that god, heaven, hell, and so on are really metaphors. Needless to say I, saw the light. Twice actually. I understood the nature of religion, and how damn smart and intelligent comedians are.