Adam Rooney was the Robins' star, netting a double to add to efforts from James Collins and Massimo Luongo. Harry Davis' penalty had cut the deficit to 3-1.
The Alex boss praised his team for creating chances, particularly after half-time, as he looks to prepare a youthful squad for a renewed effort next term.
"We needed to look at our youngsters to see if they were good enough for next season," said Davis.
"The Swindon goalkeeper could have been sent off but there are no excuses for losing the game in the first 20 minutes or so.
"We did not deal properly with their first goal and then conceded two gifts. It was better in the second half and in goal terms it was 1-1 but there were enough chances at both ends for Swindon to have won 7-5.
"We had lots of chances but we have to learn to keep working. Even so, with five key players out, our average age was 20.
"Overall, it was a hard night and there were some indifferent performances from some of our players but I would have been more disappointed if we had created nothing."