It's certainly common to cut these pills in half, and they cut quite easily. Quarters should also be doable, but I haven't tried that. Pill cutters are available from pharmacists, or you can improvise something.
Barry: Cialis is a common ED drug along with Viagra and Levitra. It is said that they give you erections, but that may be a myth
A low dose like 5mg will not give an erection, but is supposed to enhance blood flow to the area and so aid recovery. However opinions are divided as to how effective it really it.