round method fails when columns are CategoricalIndex of IntervalIndex
#### Code Sample, a copy-pastable example if possible

```python
cols = pd.interval_range(0, 2)
data = np.random.rand(5, 2)

df = pd.DataFrame(data, columns=cols)
df.round() # works

cols2 = pd.CategoricalIndex(cols)
df2 = pd.DataFrame(data, columns=cols2)
df2.round() # fails

TypeError: No matching signature found

```
#### Problem description

The `round` method fails whenever the columns are CategoricalIndex made from an IntervalIndex. The `pd.cut` function creates these types of value and they can appear in columns when using `pivot_table`.


#### Expected Output

Should round as normal.


#### Output of ``pd.show_versions()``

<details>

INSTALLED VERSIONS
------------------
commit           : None
python           : 3.7.3.final.0
python-bits      : 64
OS               : Darwin
OS-release       : 18.7.0
machine          : x86_64
processor        : i386
byteorder        : little
LC_ALL           : None
LANG             : en_US.UTF-8
LOCALE           : en_US.UTF-8

pandas           : 0.25.3
numpy            : 1.17.3
pytz             : 2019.3
dateutil         : 2.8.0
pip              : 19.3.1
setuptools       : 42.0.2.post20191201
Cython           : 0.29.14
pytest           : 5.3.1
hypothesis       : None
sphinx           : None
blosc            : None
feather          : None
xlsxwriter       : None
lxml.etree       : 4.4.2
html5lib         : None
pymysql          : 0.9.3
psycopg2         : None
jinja2           : 2.10.3
IPython          : 7.10.0
pandas_datareader: None
bs4              : 4.8.1
bottleneck       : None
fastparquet      : None
gcsfs            : None
lxml.etree       : 4.4.2
matplotlib       : 3.1.2
numexpr          : None
odfpy            : None
openpyxl         : 3.0.2
pandas_gbq       : None
pyarrow          : None
pytables         : None
s3fs             : None
scipy            : 1.3.2
sqlalchemy       : 1.3.11
tables           : None
xarray           : None
xlrd             : 1.2.0
xlwt             : None
xlsxwriter       : None

</details>
