transformer wires

[gla1013]

Should extra power and output transformer wires that are not needed go to ground ?

[JHow]

If you are talking about extra taps on secondaries, or an unused 5V secondray, generally, not.

Trim exposed wire portion, cover end with heatshrink, tuck out of the way.

[Bruce / Mission Amps]

Should extra power and output transformer wires that are not needed go to ground ?

No never, unless it is the one wire from the OT that needs to be grounded to complete the circuit or the one wire on the PT that is called the frame ground.
Since those wires are NOT the ones you called "not needed" then the answer is actually no never, period!