"The pound won’t be round for much longer" is a pretty awful tagline, I'm not sure they realised what this sounds like...
edit: oh yeah I see it now
"The pound won’t be around for much longer"
so the original sentence is sort of a pun. Maybe "around" is a local use of English.
BTW: dodecahedron is the solid object, dodecagon is the 12-sided polygon. D&D style dice as currency would be pretty awesome but it might make it difficult to resolve dilemmas using pocket change.