Milwaukee trailed 5-2 in the eighth but came up with three runs to tie the score, highlighted by Jean Segura's two-run triple.
Brewers center fielder Carlos Gomez preserved the deadlock in the top of the ninth when he robbed the Reds' Jay Bruce of a potential three-run homer off Jim Henderson (4-5) with a sparkling catch at the fence.
That set up Halton's solo blast in the bottom of the inning against Zach Duke (1-1).
Starter Bronson Arroyo surrendered two runs on three hits and four walks over 6 1/3 innings for the Reds, whose lead over Washington for the second National League wild-card spot dwindled to 4 1/2 games.
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