Business Storing Cash in the Safe Deposit Box Time for a SAR?

We have a restaurant customer who does not deposit cash to their account. They do however, exchange cash for $100 bills and then enter their safe deposit box. This customer has told a commercial lender that this is how they operate their business (it is an oriental restaurant), supposedly this is normal for this type of business. They also said they use the cash to go to a different bank and wire money to suppliers. It has become apparent they are having a difficult time closing the box and have rubberbanded it together to fit it back into the vault. Our question is whether this behavior in itself is suspicious and should we be filing a SAR? The cash exchanges are always less than $10,000.