Swiss invoices and cash payments are rounded to 5 centimes (Rappen). WooCommerce calculates to the centime, so totals like CHF 29.93 end up in orders, invoices and the accounting software.
This plugin adds the difference as its own line “Rounding to 5 cents” (for example -0.02 or +0.02):
The rounded total only helps if it also arrives in the accounting software. For shops that use KLARA or AbaNinja there are paid connectors from the same developer that create every order there as an invoice, with the same rounded total: KLARA shop connector and AbaNinja shop connector. The links are also shown on the Plugins page and below the label setting. The plugin itself does not contact any external service.