Unless there is issue with background check or the person looks totally crazy. Offer is set by the manager because it comes out of the departmental budget which HR doesn't manage. However, HR has a bigger influence in raises and counter offer to retain existing employees.
When it comes negotiating, sometimes there is room within 3 to 5%. But if you really want the job it might not be worth to risk it. I don't suggest people negotiate things like vacation days, phone bills flexible schedules etc because these are company wide policies that are out of control of hiring manager. HR and manager will back off due to these demands that make you look like a prima donna.
My two cents.
