US Dollar and Cents doesnt have different symbols.
What is the need?
How about branding millibit and microbit for now ?
1000 millibit = 1 Bitcoin
So if there is 1 Bitcoin in your account its 1000 millibit
So
millibit = 0.001 bitcoin
microbit = 0.000001 bitcoin
nanobit = 0.000000001 bitcoin so on and so forth
femtobit,
attobit,
zeptobit
yoctobit
As of now only millibit and may be microbit will be relevant
1 millibit approximately equal 4.3 USD
1 microbit will be 0.43 cents
2.32 microbit approximately equal 1 cent
232 microbit approximately equals 1 USD