I've previously written about the Exact Change Insister.  This person will do anything to make sure they pay for their $5.78 sandwich with exact change, holding up the line in the process.  They are illogical, they waste time, and they piss off everyone behind them in line.  The following are a couple of things business owners can offer that tend to counteract the negative effects Insisters:

1. Efficient single-line systems:  Single lines with multiple cashiers are almost always a more efficient way to check out customers, compared to multiple lines, multiple cashiers. Single-lines don't necessarily decrease the overall wait time for all customers (due to the lost time traveling from the central waiting point to the next available cashier).  They will also cause some customers to have a longer individual wait time. That said, they are still a better system because they bring down the maximum potential wait time for every customer.  In other words, everyone will have to wait a little bit, but no one will get individually stuck behind an Exact Change Insister because there's always another line waiting to open up.

2. Benevolent-Rounding Cashiers:  These are the cashiers that take your $10 bill for your $8.01 purchase and very quickly give you $2 change.  They understand that the act of giving the customer one penny off, and paper-bill change is worth much more than one penny to them in the long run.  Along with the time saved, this kind of benevolent rounding usually results in a more loyal customer base.

Thank you soup place in Grand Central.  Thank you deli on the corner near work.  You are doing your part to make the world a better place, and I appreciate it.