I want to round a series of numbers to the nearest price point of 5 or 9
pence (up or down). E.g. £12.74 would become £12.75, £12.78 would become
£12.79, £12.91 would become £12.89

Any ideas? I'm happy to use a series of calculations if there is no single
function that will do the trick.

TIA,

Chris.