Hi,
yes, you can insulate the the 5V tapping and just ignore it.
Is the 5V tapping connected to the others or a separate winding?
Are the 24V tappings connected together or separate windings?
If they are connected you have a centre tapped secondary and must use a single rectifier to generate your +-V for the chipamp.
This is different from many of the chipamp PSU schematics, but all of them can be made to work with a centre tapped transformer.