False pass when --fail-under=100 and codebase has >4k functions

### Environment

- `interrogate` version(s) (`interrogate --version`:1.7.0
- Operating System(s): Linux
- Python version(s):3.10

### Description of the bug
interrogate will falsely pass when --fail-under=100 when there are missing docstrings if the number of functions is high enough (n>=4000).

### What you expected to happen
If --fail-under=100, I expect a failure if there are ANY missing docstrings no matter the amount of functions in the codebase.

### How to reproduce (as minimally and precisely as possible)
1. Make a file with 4000 functions (all of which have docstrings) and run interrogate with --fail-under=100, this should pass.
2. Remove 1 docstring, run interrogate with --fail-under=100, this will still pass even though it should not (because there is a missing docstring).

### Anthing else we need to know?
I am fairly confident this is an issue with rounding when using --fail-under. I would suggest either making an exception for 100 (no missing, no rounding) or allow user to set something to fail if ANY function is missing docstring.