1) In lowball, a 10-5 hand.
2) In high, two pair, 10s and 5s.
3) In hold 'em, a 10 and 5 as one's first two cards.
4) Any game in which 10s and 5s are wild.
5) A nonstandard hand sometimes given value in a private or home game, five cards 5 to 10 with no pair, which ranks above three of a kind and below a straight. For all definitions 1 to 4, also called dime store; for definitions 2 and 3 only, sometimes also called dime stores.
Comes from the F. W. Woolworth retail chain, individual stores of which were often called five-and-ten-cent stores or five-and-dime stores (and often shortened to dime stores).