I am wondering if all 8 wires on a cat5e cable are used for
Ethernet purposes, and if that is not the case, is there a couple I
could use for phone. That way I could save $$ and time by running one
cable instead of two.

No all 8 wires are not used. An Ethernet patch cable has only 4
conductors - there should be a hint in that.

Just to jump into the middle here...

Gigabit ethernet DOES use ALL eight wires...

Even if you only do 100mb networking, having phone on the unused pair will
still introduce noise and degrade your network.

Pull a separate line for telephone! Do NOT mix your networking with any
other signals on the same bundle.