Actually, that is just one snapshot in time. In the old days, money was judged by weight. At one time, 243 of the then current silver pennies weighed one pound, hence the 'Pound Sterling'. This was rationalised to 240, probably to make the arithmetic easier (!)
The crown was known as a dollar for the reason that it was approximately the same in value, i.e. 4 dollars to the pound. Been a few devaluations since then!
The guinea was a foreign coin, I believe brought into the country as a result of raids on Spanish shipping. It was slightly heavier than the gold Sovereign, and therefore worth just a little more.
The florin was introduced in the 19th century as a first step in decimalisation
Thrupenny bits came in two forms, one 12-sided and brassy, and the other a small silver coin. I can just remember them being in use, as well as farthings.
If you were a shopkeeper or similar, it was common to have a book with multiplication tables for a selection of amounts (Quick, what's the cost of 17 items at 2s and thruppence three farthings each?)