PORTLAND — Old Port shops are donating a portion of their sales on Saturday to a local charity as part of Portland’s Downtown District’s annual Shop for a Cause Day.

The event is an opportunity to promote Portland’s local, independent businesses while supporting less fortunate members of the community, said Janis Beitzer, the Downtown District’s executive director.

This year’s donations will go to The Homeless Outreach and Mobile Engagement Team, a program led by Portland’s nonprofit Milestone Foundation.

HOME Team workers walk the streets of Portland, offering assistance to people with mental health problems and drug and alcohol dependency. The group also provides transportation for people who accept help.

Some 45 downtown shops are participating in the effort. Beitzer said shops will donate between 5 and 10 percent of their Saturday sales to the cause.

A different charity receives help every year. In 2009, PDD raised about $4,500 for The Florence House, which houses homeless women.

PDD has promoted the event in magazine and newspaper advertisements, including some in The Portland Press Herald, and in radio ads, said Beitzer.

Dean Cole, owner of D. Cole Jewelers on Exchange Street, said participating in the program is part of being a good member of the community.

And he said customers like it.

“People are looking for a way to combine their spending with something that makes them feel good and is a worthwhile cause,” he said.

Cole added that the program may, or may not, drive additional sales.

But, he said, “If someone on the other end gets something, then we are happy.”

Beitzer said PDD’s members vote each year on a different charity.