Ok.
I did exactly that for the vanity in the kid's bathroom; used a two part epoxy to cover the pennies and create a smooth surface.
I still contend you could use a poly over the pennies, you'd just have to deal with shit getting in the grooves, sorta like grout lines on the FUCKING BASTARD OF A TILE FLOOR IN MY KITCHEN!!!
Whew, that kind of snuck up on me there.
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