) -- Selling enough cut-rate merchandise -- much of it priced at a buck -- can be a lucrative business, as

Dollar Tree

(DLTR) - Get Report

continues to prove.

The discounter doubled its profit in the second-quarter and upped its full-year guidance, sending shares climbing nearly 6% to $50.64 in the first half-hour of Wednesday's regular session.

During the quarter the company earned $56.9 million, or 63 cents a share, compared with $37.6 million, or 42 cents, in the year-ago period. Analysts expected the company to earn 54 cents a share.

Sales jumped 12% to $1.22 billion, while same-store sales climbed 6.8%.

Looking ahead, Dollar Tree expects third-quarter earnings in the range of 58 cents to 64 cents a share. For the full-year, the company now forecasts a profit of $3.10 to $3.25, up from prior guidance of $2.75 to $2.90 a share.

Earlier in the month

99 Cents Only Stores (NDN) swung to a profit in its second quarter

as same-store sales surged 23.6%.

-Reported by Jeanine Poggi in New York.

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