StormWorld, for the most part, uses a universal valuation of coins as arbitrated by The Trade Guild. While this practice is obvioulsy most concentrated in the remnant cities, the surrounding economies are impacted. The further and further you go away from major trough points, centers of trade or the cities the more and more the barter system becomes far more predominant.

The base unit of measure is the copper piece, for every day transactions.

Larger transactions for business or between nobility or businesses is the Silver piece.

Gold is the coin of kindoms or City-states.

Taxes

You are going to pay them so please don't be shocked.

10CP = 1SP

20SP = 1GP

From here it gets into financial products (gems, Letters of Credit, trade bars...)