oshare 御洒落

or alternatively "shareta"

About clothes :
smart, smartly dressed, fashionable, fashion-conscious, tasteful, stylish, dressy, well-dressed, neat, snazzy, voguish, modish, chic, elegant, trendy, with-it, ritzy, up-to-date, up-to-the-minute, spruce, trim, natty, snappy, out of a bandbox, dandy, fob, coxwomb, beau, be a sharp dresser...

Japanese has adopted several of the above English words to fill the gaps of nuances. Those that are used are : chic, elegant, smart, fashion, vogue and style. There is the Japanese word 流行 (ryuukou) that also means "in vogue" or "fashionable" and proably a few others, but to talk about a person dressing well or caring about their look "oshare" is the most common.