Getting the float right is unglamorous but it is what makes end-of-shift reconciliation meaningful. If the opening amount is guessed or not recorded, the closing count cannot be compared to anything, and any shortage is invisible.
Keep the float consistent — the same amount every day, in a known mix of notes and coins. A fixed float makes discrepancies obvious immediately, whereas a float that changes daily gives cover to small, repeated losses.
Mid-shift cash movements need recording too. Money taken out to pay a supplier, or added because the drawer ran short of change, will otherwise look exactly like a discrepancy at close.