Nouns ending in -aie, -oue, or -eue are feminine.
The whole family: -aie, -oue, -eue. All feminine.
Is monnaie masculine or feminine?
lamonnaie
The rule behind it
94.4% of -aie / -oue / -eue nouns are feminine
In context
Je regrette, je n'ai pas de monnaie.
I'm sorry, I don't have change.
Excusez-moi, mais je n'ai pas la monnaie.
Forgive me, but I have no change.
Je n'ai presque plus de monnaie maintenant.
I'm very low on change right now.