§ 106-a. Service charge for receiving, handling and disbursing funds and coupons. The fiscal officer of the political subdivision or of a district therein shall impose upon each contractor such service charge for receiving, handling and disbursing funds and coupons pursuant to § 106 of the political subdivision may provide by local law or ordinance. Such service charge shall not exceed a reasonable amount which is generally consistent with charges by a bank or trust company for such a service. This section shall not apply where a political subdivision or district therein has entered into an agreement with a bank or trust company pursuant to section one hundred six of this article.