(Corrects to clarify Bayer has changed the household version of Roundup and not phased out sales of the household version in paragraph 15) By Peter Hobson CANBERRA (Reuters) -An Australian court on Tuesday heard closing arguments in a class action lawsuit alleging that a weedkiller produced by Bayer caused cancer, the first such case in Australia to reach this stage. Bayer has already paid billions of dollars to settle claims that exposure to its glyphosate herbicide, Roundup, damaged health, in most cases by causing non-Hodgkin lymphoma, a blood cancer. The company faces more than 50,000 clai…