Helfen as an auxiliary verb with a dependent infinitive
Hi MarcoPlumley, I think I can help you with this problem.
First let me fix the translation errors:
Ich helfe das Geschäft zu gründen. (I am helping to establish the business)
Ich habe geholfen das Geschäft zu gründen. (I helped to established the business)
The reason why "das Geschäft" is not in dative case is because you are not helping the business, rather you are helping someone else that is not mentioned explicitly in the sentence.
Let me change it so you can see why:
Ich helfe meinem Freund das Geschäft zu gründen. (I am helping my friend to establish the business)
Ich habe meinem Freund geholfen das Geschäft zu gründen (I helped my friend to established the business)
As you can see "meinem Freund" is in dative case and "das Geschäft" is in accusative.
The dative is used to indicated the indirect object of the verb.
There are certain verbs that require the dative. "Helfen" is one of them.