How many bundles of shingles (3 bundles per square) needed to cover a new constructed roof without a starter course. The roof has a 5/12 slope.

No idea, you did not tell us the size of the roof, what is the width and length of the roof. Are there porch areas.

Are you wanting to keep a couple of full bundles extra so you have matching shingles for repairs latter.
What you are using for a starter course?

Roof has the dimensions: 32' long, 28' long, 27' wide,25' wide with a 5/13 slope. How many bundles of shingles (3 bundles per square ) is needed to conver a roof with the dimensions given? Not calculating for a starter course for shingles.