A security deposit shall not be required except for the purpose of securing against loss of or damage to real or personal property or payment of money due to the supplier or credit extended to the dealer. Any security deposit required of the dealer may be satisfied by a letter of credit or the deposit of cash or a pledge of a savings account or its equivalent in a banking institution located in Minnesota. In the event that the security deposit is made by the dealer by depositing cash with the supplier, the deposit shall earn interest at the rate of six percent per year which shall accrue to the benefit of the dealer and be payable to the dealer upon termination of the security deposit, less any charges to which the supplier is entitled to collect from the security deposit or interest earned on it. In the event that the security deposit is made by the pledge of a savings account, a savings account shall be opened in the joint name of the supplier and the dealer and neither party shall be entitled to withdraw the funds without the consent of the other party; upon termination of the security deposit arrangement, the principal deposit together with accrued interest at the rate paid for the account shall be payable to the dealer after deduction of any charges to which the supplier may be entitled.