Pandas function with multiple conditions - Value error

I am trying to create a function with multiple conditions. This would add new column with a calculated amount. Part of it is below.

I have looked at other answers but can't work out what is wrong.

# import modules
import pandas as pd
import numpy as np

#data
data2 = pd.DataFrame({'Unit of Measure' : ['EA', 'EA', 'AA'],
                     'round' : ['no', 'yes', 'no'],
                     'add_gst' : ['no', 'yes', 'no'],
                     'Unit Charge' : [1.8, 2.5, 3.0],
                     'Time Units' : [1.0, 1.5, 2.0]})

# function
def include_gst(df):
    rounded = 0.0
    if(data2['Unit of Measure'] == 'EA' and data2['round'] == 'no' and data2['add_gst'] == 'yes'):
        rounded = data['Unit Charge'] * data['Time Units']
        rounded = rounded.round(2) # to two decimal places
        rounded = rounded * 1.10 # add gst
        rounded = rounded / 0.05 # round to nearest five cents - step 1 - divide by 0.05
        rounded = rounded.round() # round to nearest five cents - step 2 - to nearest integer
        rounded = rounded * 0.05 # round to nearest five cents - step 3 - multiply by 0.05
        return  rounded
    else:
        return 1.0

data2['incl_gst'] = data2.apply(include_gst, axis = 1)

Error:

ValueError: ('The truth value of a Series is ambiguous. Use a.empty, a.bool(), a.item(), a.any() or a.all().', 'occurred at index 0')

It would be good to get it to work. Thanks.