This pull request corrects a critical issue in the calculation of employment bonuses for employees in Belgium, ensuring compliance with specific tax regulations. The fix adds the necessary rounding steps required by Belgian law, preventing inaccurate bonus amounts and potential tax discrepancies. This update directly addresses a documented requirement for accurate reporting.

The employment bonus computation was missing two roundings steps that are explicitely asked for in the following documentation: https://www.socialsecurity.be/employer/instructions/dmfa/fr/latest/instructions/deductions/workers_reductions/workbonus.html