Moving away from finger rolls and toward coin manipulation in general I like to be able to do coin tricks with whatever a client has in their pocket/handbag. Although phrases such as 'a bigger coin will make it easier for you to see everything' tend to steer people away from 5p/1p.
Go to Las Vegas if you want silver dollars. Not much use in the UK so I don't tend to use them but occasionally a client will give me something unusual to manipulate.
Nigel