In the US (perhaps elsewhere) "ta-tas" is a slang term for breasts - "Check out the bodacious ta-tas on that girl! " It's not very likely to lead to confusion with "ta ta" for "goodbye" - unless you're dealing with a teenager, in which case "ta ta!" More @Wikipedia
Hover over any link to get a description of the article. Please note that search keywords are sometimes hidden within the full article and don't appear in the description or title.