To terminate a bundle of CAT5 cables that have not been labeled, which tool can be used to distinguish between cables and how?

A Toner Probe will do the job.

if the cable is Far from each other. Mount the2 Aligator clip to any of the eight wires of a cat5 separately and and trace those cable with the probe on the other end. label the cable having the same amount of sound is sounding from the probe device.

if cable is Near to each other.Remove the skin of a cat5 cable you want to trace and connect them all by twisting and connect the black aligator clip to it, go to another end and connect the the red aligator clip to each cable, if the LED indicator lights up then thats it.

tone generation

Using a Fox and Hound. One end of the cable is connected to a device that either by sound or light confirms when the other device completes the circuit.