SOAPUI 5.4.0 JSON Assertion of Double Values Ending .00

I am running SoapUI 5.3.0 and I confirm that your script does not give an assertion error for me.

assert GroovySystem.version == "2.1.7"
def slurper = new JsonSlurper()
def json = slurper.parseText '{"accountBalance":{"value":125755.00,"currency":"CAD","amountType":"DEBIT"}}'
assert json.accountBalance.value.toString() == "125755.00"

It looks like JsonSlurper had significant work done to it in Groovy version 2.3 (http://groovy-lang.org/releasenotes/groovy-2.3.html). Then the below using the groovy console at https://groovyconsole.appspot.com/ 

assert GroovySystem.version == "2.4.4"
import groovy.json.JsonSlurper
def slurper = new JsonSlurper()
def json = slurper.parseText '{"accountBalance":{"value":125755.00,"currency":"CAD","amountType":"DEBIT"}}'
assert json.accountBalance.value.toString() == "125755.00"

Assertion failed: 

assert json.accountBalance.value.toString() == "125755.00"
       |    |              |     |          |
       |    |              |     125755     false
       |    |              125755
       |    [amountType:DEBIT, currency:CAD, value:125755]
       [accountBalance:[amountType:DEBIT, currency:CAD, value:125755]]

	at Script1.run(Script1.groovy:5)

I would suggest that the newer behaviour is probably still correct. The JSON data defines a number, not a string. In theory, all we should care about is

assert json.accountBalance.value == 125755

If the application you are testing really does care about the decimal places, that would be non standard. Otherwise the data should be a string.  But since it isn't, you might need to do some non standard parsing.

def json = '{"accountBalance":{"value":125755.00,"currency":"CAD","amountType":"DEBIT"}}'
assert json =~ /"value"\s*:\s*125755.00/