Given that this is an error in principle applied, I would check the numbers again against the finance company’s statements. If you have been credited by them for exact principle amounts due, and paid off the amount they told you was required to fully discharge the loan, a rounding error seems unlikely.
But, if you finally decide it is accumulated rounding errors, use a journal entry. Debit the loan account for the 6 cents and credit a miscellaneous income account. The finance company says you have paid the loan, but you think you still owe 6 cents. So that is income.