I write 5 zł (5 zlotys, 5 PLN) or 5€ (5 euros, 5 EUR) because in Europe we don't unnecesarily invert the currency symbol compared to what we speak. The following system, which I found on Wikipedia, would make the most sense:

Exceptionally, the symbol for the Cape Verdean escudo (like the Portuguese escudo, to which it was formerly pegged) is placed in the decimal separator position, as in 250.

That'd be perfectly consistent with what we speak and solve the problem of fractional currency notation as well.