I know that stocks below $1.00 can be traded to 4 decimal places, but is that possible for stocks above $1.00? On a list order transactions, one can find prices like $2.2801 despite most ecn brokers forbidding the practice.
I'm not sure fennec's answer is the right one.
This happens too frequently to me in thinly traded stocks. I will have a bid of say 2400 shares @ $1.06 outstanding as the listed high bid price and quantity. Suddenly a trade for 200 shares will execute at 1.0601 leaving my offer untouched.
Once in a blue moon is one thing; 25 to 30 percent of the trades and always at $0.0001 above or below my price is another. I suspect someone is "stepping in front" of me. A broker practice forbidden but which seems to happen all too frequently.
For example watch SPPR. Yesterday (10/4/12) at the close, Scottrader listed the high for SPPR as 1.0701 and the low as 1.0699. (Note: Many sites round the data to 0.01; don't be misled.)
It's possible that if someone bought, say, 300 shares, they were able to buy 200 of them at one price, but then had to pay a slightly higher price (say, $0.01 higher) for the next 100. Then the price reported for those shares would be the average amount, and would be fractional.