CANNY: (adj) = Careful and shrewd, especially where one's own interests are concerned. Cautious in spending money; frugal. Scots.: Steady, restrained, and gentle. Snug and quiet.
Having or showing a clever awareness and resourcefulness in practical matters: astute, cagey, knowing, perspicacious, shrewd, slick, smart, wise. Informal savvy. See ability/inability, careful/careless. Careful in the use of material resources: chary, economical, frugal, provident, prudent, saving, Scotch, sparing, thrifty. See careful/careless, save/waste.

“XYZ strikes a canny deal, but [you] don’t pig out on the shares - Times Online.”

“Q.: Could you say whether the adjective canny, being used in relation to the third person, a negative or positive reference (in the modern English)? Or it entirely depends on the tone? (In this case, how would you understand its positivity if it’s just written in the informal description?

A.: Canny to me has a suggestion of cunning. To my mind there isn't really a perjorative undertone. Funnily enough I have just heard it used on the BBC Radio 4 Today programme. As I was half asleep I didn't quite catch the context but there was no 'negative' suggestion. Another similar word is 'crafty'. When we use these adjectives to describe someone who is being cunning/crafty/shrewd we say it also with a hint of admiration for the person. For some reason I associate the word as follows: A canny Scot. The Scottish people have a reputation for being careful with their money mainly because over generations they have had a hard time earning a living from a barren land. In fact they are the one race that has sought work in other countries more than many others.” (http://www.english-test.net/forum/ftopic14011.html)

cannily can'ni·ly adv.canniness can'ni·ness n.

UNCANNY = Peculiarly unsettling, as if of supernatural origin or nature; eerie. See synonyms at weird. So keen and perceptive as to seem preternatural.
Veja que existe também esta forma [old Scot] que não tem nada a ver com a palavra acima: Ye canny [verb: cannot] come in here wi'oot yer troosers pal!
Source: Your Dictionary