Screwfix has raised more than £10,000 in just four months for the Everyman prostate and testicular appeal.
The funds were accumulated a few pennies at a time by customers making 50,000 spare change donations via Pennies, the electronic charity box.
Screwfix added Pennies to its website earlier this year, allowing customers to round up their total order to the nearest pound with the extra pennies going to the Everyman appeal and other UK charities.
Screwfix marketing director John Mewett said: "The Pennies initiative is a new channel for an old habit. Gone are the days in which the only way to raise money was to drop a few coins into a charity box on a shop counter as now customers can easily donate a few extra pennies when they pay by card.
"The initiative is a really simple and sustainable way to offer our ongoing support to Everyman."
He added that nearly 4,000 customers are rounding up their purchases each week, bringing in more than £800 for charity.
Screwfix has been working with Everyman since 2009, raising funds for the appeal set up by The Institute of Cancer Research in 1997 to eradicate testicular and prostate cancer.
Everyman receives 75% of donations to Pennies. The remaining 25% will be shared amongst other charities, including Shelter, Together for Short Lives and the Children's Burns Trust.