There are specific HSE regulations that cover the use of Display Screen Equipment (DSE). This covers the use of any computers or equipment with display screens, such as electronic tills.
These include making sure staff are comfortable when using them, in other words they should be set at the correct height and angles to make sure staff do not risk getting eye strain or any Repetitive Strain Injuries (such as problems with wrists or arms, e.g Tenosynovitis or Carpal Tunnel Syndrome)
It is important to make sure screens are adjustable and are the correct distance from the operator. Where staff are seated the chairs should be adjustable, and foot rests and wrist rests may be appropriate.
More details can be found on the HSE Website: https://www.hse.gov.uk/pubns/priced/l26.pdf