Most shops will remain closed until next Monday, with banks and Government offices around the State reopening on Tuesday.
Dublin's main department stores, such as Clerys, Arnotts and Brown Thomas, will reopen on bank holiday Monday.
Some supermarkets, including Superquinn and certain Tesco branches, will open for a half-day today. Most other supermarkets, including Dunnes Stores and Marks & Spencer, will remain closed until Monday.
Many large shopping centres, including the St Stephen's Green Centre, The Square in Tallaght and the Blanchardstown Centre, will also be closed for three days until Monday.
Waterstone's bookshop in Dublin will be open from 11 a.m. to 5 p.m. today, but will remain closed on Saturday and Sunday. Hodges Figgis' bookshop in Dublin is closed today but will open on Sunday from noon to 6 p.m.
Mr Sean Rippington of Dublin City Centre Business Association, which represents some 135 businesses, said retailers were "very pleasantly surprised at how quickly shoppers returned to the shops after Christmas."
He said pre-Christmas takings were up by an average of 20 per cent on last year, but the turnout for the sales had also been strong.
"Everybody is pleased with how it has gone since Christmas, because most thought all the money had been spent. Lots of the money is coming from the North."
Mr Rippington said many shops would be making additional reductions to their sales merchandise from next Tuesday.
"After the initial bargains, the second phase of reductions will start. I'd say as of next Tuesday it would be well worth revisiting the sales," he said.
Banks will be closed on bank holiday Monday and reopen on Tuesday, January 4th. Local and central government offices will also reopen next Tuesday.
Meanwhile, as customers seized their last chance to stock up on champagne, off-licences reported unprecedented sales.
At Dunnes Stores in the St Stephen's Green Centre, the off-licence manager, Mr Vincent McMullen, said champagne sales were "absolutely bananas".
"I never imagined anything like this could happen. On any normal year people are looking for a good bottle of sparkling wine for £10.
"This year, we sold out of our own millennium champagne on Christmas Eve and since then it's been Moet et Chandon at £25.49 for a bottle of non-vintage.
"People are buying by the case. For every person who buys a bottle, three ask for a magnum. The last magnum of champagne I had went 2 1/2 weeks ago."
Mr McMullen said 150 bottles of champagne were sold yesterday. Last week champagne accounted for 12 per cent of the off-licence's sales, he said.
At Whelans off-licence on Dublin's Wexford Street, Veuve Clicquot was the favoured drink, costing £29.99 per bottle.
"We sold out of the bottles a couple of days ago, but we still have magnums left," said a staff member.