You spelled 8 dollars correctly.
The currency value $28 or $28.00 is written twenty-eight dollars.
Eighty-eight dollars.
eight hundred and forty dollars
sixty eight dollars
The currency amount $68 is "sixty-eight dollars."
Eight hundred and ten dollars.
Five hundred and eight dollars.
The currency amount $68.00 is "sixty-eight dollars" (and no cents).
one hundred and forty eight dollars
Eight hundred and fifty nine dollars.
twelve hundred forty-eight dollars
Ninety-eight dollars and three cents