A fingerprint scanner provides the highest level of security and there is absolutely no way to cheat this system. This really is the ultimate in EPoS security.
With a finger print reader you can be 100% certain that it is impossible for any of your staff to sign on as a different user.
It is a one off investment and you will not incur any additional costs for extra cards or key fobs.
However, this is also the most expensive security option available and is likely to cost in excess of £200 per scanner. You should also ensure you have a log in code assigned in case the finger print scanner fails.