Hi, if you dig, like E14 or RS parts suppliers you can get 10V caps.
Don't use 5.6V on 5V, to close to rated tolerance.
I have the job of repairing 3phase current monitors, they have a 5V rail and all the 6V electrocaps have got bigger and failed.
No skin of my nose, 6 caps per monitor times 150 monitors, good earner for me, pain in rear end for customer.
Tom..... 