I work for a music & film distribution company.
We were happily using Linux diskless computers with Epson miniprinters
as point-of-sale systems in our retail stores, until my
country's government decided to make the use of officially
approved fiscal cash registers mandatory. We still wanted
to use computers, not cash registers in our stores so we
purchased cash registers that came with serial interfaces,
and we hooked them up to our computers replacing the miniprinters. I wrote a driver for
them in Perl so now the clerks can still use the sales
software they're accustomed to, but the receipts come out
of a cash register instead of a printer. Basically, the
cash register now acts as a printer via keyboard emulation.
It even works in a network environment, i.e. several
computers can print receipts on a single cash register.