The pound was divided into 240 pence, or 20 shillings. So, 10 shillings is half a pound. 4 pence is 1/60th of a pound. So it's more "rounded" than it might s

The pound was divided into 240 pence, or 20 shillings. So, 10 shillings is half a pound. 4 pence is 1/60th of a pound. So it's more "rounded" than it might seem. Much like how 3, 6, 9 and 12 feet are potential rounded values measured in feet; traditional units are another semi-duodecimal system. (This system remained into use until 1971.) These fines would have been paid in coins. 10 shillings is a specific coin: gold half-sovereign. At the time (I think) the fine could be paid, potentially, with just three coins: one half-sovereign, one sovereign, and one groat/fourpence. The inclusion of the relatively small amount fourpence amount, which is silver and not gold coinage, is perhaps symbolic of something but I don't know what.