good and simple way to differentiate 100 tenants

when you have many tenants and they all have same kind of units and same rent, you still can have your tenants make direct deposit to your account and you still can identify who paid and who not by doing this: ask each tenant pay little different amount like this:

tenant            rent
1                    700
2                    700.01
3.                   699.99
4.                   699.98
5.                   699.97
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