I'm a bit confused by what it actually means that they are calc'ing it to 10 decimal places. When I first heard they were doing this, I assumed that they'd occasionally drop a penny off their fees, to keep the tally in check, but it's not happening.
For example, I have a loan that charges 0.02 / month, every month, for the past 12 months. I hover over, and I see the fee is actually 0.016679700 ...
So, if I do that math month by month, looking at the total fees:
1) 0.0166797 actual, 0.02 charged
2) 0.0333594 actual, 0.04 charged
3) 0.0500391 actual, 0.06 charged
4) 0.0667188 actual, 0.08 charged
etc ...
From the looks of that, I'd expect about every 3rd payment to be 0.01 instead of 0.02, to keep the total cost inline, but it's not happening. So, as I see it, they are still overcharging on fees on the month-by-month basis. They used to handle this by making a lump sum fee reimbursement at the end of each loan. Not sure what they doing now.