I wrote a long post on this thread but I've gone through it again twice and can't find it. So here we go again. (I hope there aren't 2 threads on the subject and I'm inadvertently posting the same thing twice...)
I was a Saturday girl in a department store so I missed out on the training that the rest of the staff had as that was on quieter days during the week.
I didn't have any trouble with it. I was doing A level maths and this was simple arithmetic.
However, I left the country for good in 1973 when decimal currency was still relatively new, so I still think of it as "new money" and have to look carefully at the coins as if I were a foreigner.
It's the same here, though. I still think of Euros as "new money" although we changed from the Deutschmark 20 years ago. I still have to check change carefully as the 2 €c and 5 €c are easily confused.