Accumulating bonus via purchases

Accumulating bonus via purchasesCategory: ReligionAccumulating bonus via purchases
AK asked 2 years ago

Salam Alaykum
I want to join a cooperative society, which has many business interests like grocery stores, banks etc. Part of the benefit of the cooperative members is to use the banking services free of charge without monthly charges and also to accumulate bonuses on purchases made with the cooperative grocery stores.  The requirement of membership is around 100 euros. But there are two options of payments
1. To pay the full membership fee of 100euros
2. To pay the minimum membership fee of 20euros, thereafter a member can pay off the 80euros balance by accumulating bonus made on purchases from the stores been operated by the cooperative society (For example, if a cooperative member purchase items of 75euros monthly, the member will get 2euros bonus at the end of that month, so the accumulation of multiple purchases bonus will automatically offset the 80euros membership fee)
 
Pls is the type of transaction halal or haram