The standard currency across the realm is called "pieces", and most come in gold, silver, and copper. Some trade kingdoms use electrum and platinum, but its not accepted at value in most cities. Some nations have their own mints of coins that are excepted instead of pieces, and in those places pieces have to be exchanged for the local currency. Each coin in every country is made so 50 of them will weigh out to 1 pound. Because of this, 5 pound trade bars can be made for larger business deals. Below is a conversion table and all the cities that use their own currency.
1 Platinum = 10 Gold
2 Electrum = 1 Gold
10 Silver = 1 Gold
100 Copper = 1 Gold
In Waterdeep they have a special minted coin called the "harbor moon" that is worth 50 gold pieces.
Platinum piece: "Suns"
Gold piece: "Dragons"
Electrum piece: "Sambars"
Silver piece: "Shards"
Copper piece: "Nibs"
Platinum piece: "Fairsail"
Gold piece: "Dragons"
Electrum piece: "See-Shees"
Silver piece: "Bults"
Copper piece: "Tharns"
In Silverymoon they have a special minted coin called a "moon" that was worth 2 gold pieces.
Platinum piece: "Unicorns"
Gold piece: "Dragons"
Electrum piece: "Swords"
Silver piece: "Shields"
Copper piece: "Glints"