U.S. retailers are reporting strong sales from this Black Friday weekend after offering some of the best deals of the holiday season, and they hope to keep that momentum going through the upcoming month.

Now that retailers have gotten customers in the stores with deep discount, they will have to keep shoppers coming in at regular prices to boost their profit margins. If they can’t, they’ll have to go back to slashing prices before the holiday, according to Bloomberg.

Retailers must walk a fine between offering attractive promotions and trying to stay profitable. They will need to minimize the discounts they offer now that the Black Friday rush is over.

A National Retail Federation report states that 140 million shoppers would hit stores between Thanksgiving and the end of the weekend before Cyber Monday rolls around, when websites offer similar price-slashing promotions. The NRF believes this holiday season will be the best in years thanks to a rebounding economy. Sales should jump 4.1 percent over last year thanks to dropping unemployment and rising wages combined with plummeting gas prices, the NRF said.

November and December are the most important months for retailers, as they account for 19 percent of annual revenue, NRF says. The name “Black Friday” is often attributed to the myth that retailers don’t become profitable — or move from red ink into the “black” until the day after Thanksgiving when shoppers rush to clear out their shelves.

President Barack Obama himself left his confines with his teenage daughters for some holiday shoping, visiting the Politics & Prose bookstore, where they purchased 17 books that included children’s stories, young-adult fiction, and “Age of Ambition,” which was a National Book Award. They also bought the literary classic “Heart of Darkness.” The trip was arranged to promote shopping at small businesses on a day dubbed “Small Business Saturday.”

Online sales picked up 14 percent on Thanksgiving day and 9.5 percent on Black Friday, International Business Machines Corp.’s Digital Analytics Benchmark reported. More detailed shopping results won’t be available until January.

Amazon.com reported a rise in sales of a whopping 26 percent on Thanksgiving and 24 percent the next day.