Use 2 decimal points for Cost, rounding up

Switches the precision of Cost from 3 to 2. The value is rounded
up as demontrated by the following block of code given the following
csv file.

```csv
Cost
123.1234
123.5678
```

```python
>>> dataframe = pandas.read_csv("csv.csv", dtype={"Cost": pandas.ArrowDtype(pyarrow.decimal128(12, 2))})
>>> dataframe
     Cost
0  123.12
1  123.57
```

Related #35

process_report/process_report.py

@@ -269,7 +269,7 @@ def merge_csv(files):
     dataframes = []
     for file in files:
         dataframe = pandas.read_csv(
-            file, dtype={COST_FIELD: pandas.ArrowDtype(pyarrow.decimal128(12, 3))}
+            file, dtype={COST_FIELD: pandas.ArrowDtype(pyarrow.decimal128(12, 2))}
         )
         dataframes.append(dataframe)