Most of the scripts have different types of issues. There are lots of companies providing cashback script just like cashback engine, cashback script but none of them i have used. Moreover, scripts has almost same design for all the website which have used it, instead of color changing option or logo changing etc (as a example you can watch cashbackengine script). This thing has a bad impact for a professional website. Suppose, 5 websites has used same script, one of them is a spamming site, than a normal user can't trust on your brand due to design/development similarities. So, i can't recommend you any script for cashback website. If want to develop a professional one than you should have to contact with digital agencies which are developing these kind of projects like iLeadDigital who's guys are working on affiliate cms design and development ileaddigital(.)com/services/web-design/affiliate-cms-development. Apart from, there are lots of others companies which you can find by using google or any other search engine. To select a company for this purpose. First make sure you have checked its portfolio and find out the relevant projects. Anyways, thanks for making the nice efforts.