The former Tottenham striker scored a hat-trick - two from the penalty spot - to take his season tally to five but was more interested in helping the Galaxy to a vital three points which saw them remain fourth on the Western Conference table.
"It's always nice to score," Keane said. "One, two, three or four doesn't really matter.
"As a striker, your job is to score goals, so it's of course great to score a hat trick, but I think the most important thing is getting the three points and bouncing back after the defeat last week against [the New York] Red Bulls, which we certainly didn't deserve to lose."
Keane provided the assist for Sean Franklin to tap home in the 12th minute after playing a neat give-and-go with Marcelo Sarvas before adding a second goal with a calm side-footed finish from a spilled ball in the 24th minute.
Ten minutes later, the Republic of Ireland skipper converted from the penalty spot on the retake after Sounders keeper Michael Gspurning had come a few yards off his line before the whistle. Keane then made it a four-goal lead on the stroke of half-time by completing his hat-trick when sending Gspurning the wrong way from the spot.