cpp/types/numeric limits/round style

The value of identifies the rounding style used by the floating-point type  whenever a value that is not one of the exactly repesentable values of  is stored in an object of that type.

Example
The decimal value cannot be represented by a binary floating-point type. When stored in an IEEE-754, it falls between $0x1.9999999999999*2-4$ and $0x1.999999999999a*2-4$. Rounding to nearest representable value results in $0x1.999999999999a*2-4$.

Similarly, the decimal value, which is between $0x1.3333333333333*2-2$ and $0x1.3333333333334*2-2$ is rounded to nearest and is stored as $0x1.3333333333333*2-2$.