Shining a Spotlight on Dubious Charges
Supposedly, right angles don’t exist in nature.
Similarly, people seldom make purchases for even amounts.
So, the grocery/gas/dry cleaning bill is almost never exactly $40; rather, it’s $39.72 or $40.17 or some such.
“That’s Odd!” (Literally)
Consumers can use that phenomenon to help thwart credit card fraudsters who — somewhat counterintuitively — are more apt to sneak thru lots of illicit small charges on many accounts (the better to escape detection), 
than to make a smaller number of more conspicuous purchases.
The strategy?
When buying something, explicitly round to even amounts.
That way, when consumers review their monthly credit card statements (Note to consumers: always review your monthly credit card statements), they can easily spot the charges (debits) for odd amounts — and take action if there’s anything suspect.
Below the Radar
The foregoing recalls a story I heard when I was a CPA in California auditing banks (a long time ago), about a details-obsessed grandma who was adamant that her bank was short-changing her.
The problem?
Every 8 months, her checking account was out of balance by exactly 1¢.
When she repeatedly called to complain, bank officials dismissed it as a rounding error — and labelled her as a crank.
“Grandma” was ultimately vindicated when the bank discovered a multi-year fraud, totaling tens of millions of dollars.
The criminals’ m.o.?
Each month, they subtracted 1/8 of 1¢ from millions of customers’ accounts that they’d hacked into.
P.S.: Thanks to Edina Realty’s Jim Young for the credit card anti-fraud tip!
