Honestly? I think it depends on what it is. People here in NZ are more accepting of cultural tattoos like moko and tatau, so those aren't as much of a problem (but often only if it is congruent with the ethnic identity of the wearer). Small tattoos on anyone doesn't seem to cause a fuss, but we did get asked in class, "Does anyone have any problematic tattoos?" heh.
I asked someone at work what the policy was and they said "just cover it up", but I see people with extensive forearm tattoos all the time. Maybe because Mental Health has a good ratio of male to female nurses so the culture is quite different from general nursing, which is more uptight.