How do I clear my Apple Account balance?

It’s not Apple Pay. The funds are in your Apple Account. Apple Pay and Apple Account are 2 entirely different services.

You’ll either need to spend it or if it’s not enough to purchase a product or service, you’ll need to contact Apple Support to have your account set to zero. As an alternative, add a payment method and purchase an item for more than your account balance. The purchase will first be withdrawn from your account and then any remaining balance with be charged to the payment method in your account.  If you’re in the US please call  1-800-MY-APPLE or outside the US, consult the support articles below.

Contact Apple for support and service - Apple Support

Change your Apple ID country or region - Apple Support

Apple Pay doesn’t have a built-in way to remove cents, but you can work around it by rounding up your tip, manually entering a whole-dollar amount (when possible), or using a bank feature that rounds transactions. If you’re sending money via Apple Cash, just type in a whole number.