The primary objective in applying 5 degrees of bank towards the live engine is to lower critical speeds (VMC). The aircraft can be controlled at a lower speed when 5 degrees of bank is applied as demonstrated in Ex Assy 2.
If the aircraft is flown wings level and the ball central with one engine inoperative, there will be a sideslip towards the dead engine. Balanced flight can be achieved by applying 5 degrees of bank towards the live engine, but now the ball will now be offset towards the live engine.
Pre-Flight Briefing Manual - Multi-Engine Course by Mike Woodgate is a worthwhile reference.