Hum, $10M in small unmarked bills.
Lets assume you mean 20's, the largest bill most people carry around. $10M is 500,000 bills. Now its about 454 bills per lbs so we're looking at 1101.32lbs of money. Can't just grab a suit case and run off with it can you? For comparison then for 50's you need 200,000 or 440.5lbs & 100's 100,000 of them for 220.25lbs. None of these are simple to transport without a vehicle.
I'm not even going to bother with figuring an even split of 1's 5's & 10's.
Oh, alright, I will:
Here's an even split by bill count:
One would need 625,000 of each bill; 1, 5 & 10 to get to $10M or 1.875M bills which weighs 3955lbs.
If you wanted an equal value for the lowest three denominations which would be ~$3.3M of each denomination which works out to ~4.33M bills or 9544.8lbs. Though you'd need to substitute an extra fiver for half of a ten since it won't quite divide up evenly like this.
In a nutshell though, cash for this kind of transaction would be a tad unwieldy unless you went with 100's even then its not easy to carry around for most people. A wire transaction is the way to go and ass soon as the money is there start moving it around splitting it up in various ways to hide the trail, etc.