Actually, you might be able to do something along the lines of what you’re looking for with linked record fields (instead of grouping records).
You would create another table that is simply designed for the purpose of keeping track of each day’s cash balance. So, each record in this new table would simply have a date and a balance.
Then, back in your original table, every time you create a new record, you would manually link to the previous day’s record from that other table, which would then lookup the previous day’s cash balance.
You would need to automate it the other way, too:
At the end of each day, your current table would need to send the nightly balance into the other table as a new record there, so it would be ready to be pulled in again the next morning.
That would likely do the trick.