Will Doing This To My Car Jack It Up? Help A Girl Out

Ok so I remember once upon a time my daddy told me never to put gas in when they are 'refilling the tanks.' My father was a wise man, so I did as I was told and didn't ask questions. Now as an 'adult' I think to myself, I never really looked into it any further....is this still true? Why did I never ask my dad why? lol

As I put gas in my car yesterday I see the guy 'refilling' and thought maybe it's time to further investigate? Is this true or just a theory or a matter of personal opinion? Since I obviously went ahead and put gas in anyway that day, does it do bad things to my car or...? Inquiring minds want to know, help a girl out.