die Kassette
cash box
A small lockable container for storing money or valuables.
Er bewahrte sein Bargeld in einer kleinen Kassette im Schreibtisch auf.
He kept his cash in a small cash box in his desk.

cassette
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cash box
A small lockable container for storing money or valuables.
Er bewahrte sein Bargeld in einer kleinen Kassette im Schreibtisch auf.
He kept his cash in a small cash box in his desk.

All meanings of 'Kassette' (cassette) derive from the idea of a small box or casing. Whether for money (m01), magnetic tape (m02), as a ceiling recess (m03), or for bicycle sprockets (m04), the basic form is always a container or cover.
Die Musikkassette ist ein kleines Plastikgehäuse für das Tonband.
The music cassette is a small plastic case for the audio tape.
In the meaning 'container for valuables', the word 'Geldkassette' (cash box) is often used. Typical verbs are 'aufbewahren' (to store), 'einschließen' (to lock up), or 'knacken' (to crack open).
Wichtige Dokumente bewahrt sie in einer feuerfesten Kassette auf.
She keeps important documents in a fireproof cash box.
When 'Kassette' (cassette) is mentioned in connection with music, films, playback devices, or the 80s/90s, it means the audio or video medium. It is often specified as 'Musikkassette' (music cassette) or 'Videokassette' (video cassette).
Mein altes Auto hat nur ein Radio für Kassetten.
My old car only has a radio for cassettes.
You can recognize this meaning from words like 'Decke' (ceiling), 'Gewölbe' (vault), 'Saal' (hall), or 'Kirche' (church). A 'Kassettendecke' (coffered ceiling) is a ceiling made up of many square or rectangular recesses.
Die Decke im Festsaal des Schlosses ist mit hunderten Kassetten geschmückt.
The ceiling in the palace ballroom is decorated with hundreds of coffers.
In sports and technical contexts, especially cycling, 'Kassette' (cassette) refers to the sprocket cluster on the rear wheel. Words like 'Kette' (chain), 'Schaltung' (gearshift), 'Ritzel' (sprocket), or 'Gang' (gear) point to this meaning.
Der Fahrradmechaniker hat mir eine neue Kassette mit 11 Ritzeln montiert.
The bicycle mechanic installed a new cassette with 11 sprockets for me.
checkout / cash register
'Kasse' and 'Kassette' sound similar and can both have to do with storing money. A 'Kasse' in a store is the device or container where money is kept when people pay. 'Kassette', on the other hand, more often means a small lockable box for money or valuables. In addition, 'Kassette' can also be an old audio or video carrier. So the risk of confusion mainly comes from the similar form and the connection to the topic of money. In a store, you normally say 'Kasse'; for a small box or an old tape, you say 'Kassette'.

Im Schrank lag eine alte Kassette mit Liedern aus ihrer Jugend.
In the cupboard there was an old cassette with songs from her youth.
Die Mitarbeiterin öffnete die Kasse und gab dem Kunden Wechselgeld.
The employee opened the cash register and gave the customer change.