In the ceremony of Pidyon HaBen, the father needs to give the Kohein who is involved, 5 Selaim.
How much is a sela in US dollars?
Mi Yodeya is a question and answer site for those who base their lives on Jewish law and tradition and anyone interested in learning more. It only takes a minute to sign up.Sign up to join this community
In this case it's intended as a weight of silver, not a currency per se. As DoubleAA noted above, half a troy ounce is your rule of thumb. (Rashi says "half an unkia in kolonia; despite having lived in Troyes, he felt the weights were more precise in Cologone, Germany.) So you'd have to do the math given current silver values what 2.5 troy ounces of silver costs -- as of today, I'm seeing $23 dollars per troy ounce, so $60 total or so? (And as it can be "cash or cash-value", you could do that math and then give the kohen just about any item with that value.)
As DoubleAA noted, some opinions have it as a little more than that, maybe more like two-thirds of a troy ounce.
Some folks do go to a coin shop and find older US currency that actually contains silver; you'd just have to do the math on its total weight of pure silver. (Back in the day -- and I think this is in Rabbi Bulka's RCA Madrich -- the typical US silver dollar didn't quite have half a troy ounce of silver, so it wound up being more like seven silver dollars.)
As I recall, the Walking Liberty Silver Half Dollar is easy to find at coin stores, and contains 0.36 troy ounces of silver. Put two of those together, and you easily have a sela of silver. (Thus, use ten for pidyon haben.)