There is no special treatment under IFRS. Here are the general entries in a petty cash imprest system:
When you first get the money for the petty cash float
DR Petty cash a/c
CR Bank a/c
When there is a petty cash expense
DR Relevant expense a/c
CR Petty cash a/c
When you reimburse the money ( when the petty cash float is going below a set limit )
DR petty cash a/c
CR Bank a/c