Alas, the many pages of tables in Collins’ Ready Reckoner book give the lie to this. Here’s the page spread for applying 10% surcharge/discount to amounts from 2½d (rounds to 1p, decimal) to 20s / £1:
Pretty ugly, and you end up using a lot of farthings (quarter pennies).
Most of the book is given over to additions of amounts because it was so complex (like 120 × 7¾d = £3 17s 6d). Even if we did divide that amount by a friendly number, you still end up with non-intuitive amounts:
£3 17s 6d ÷ 5 = 15s 6d
And to think it was kept for so long because change “would be hard on the old folks” …
Speaking of farthings be sure to check out Thomas Fowler’s mechanical ternary calculator - reduction of sums to farthings for computation and finally reconstructing pounds shillings and pence was standard practice
So, as this has switched slightly towards British money, there’s a nice video on this topic by Youtuber Lindybeige, 53min of currency history, called “Pounds, shillings, and pence: a history of English coinage”, https://www.youtube.com/watch?v=R2paSGQRwvo
