JOHANNESBURG (Reuters) - South Africa's rand firmed against the dollar on Wednesday, tracking a stronger euro after a successful Treasury bill sale in Greece raised hopes the debt-ridden euro zone member would avoid a default. The market will be keeping an eye on local retail sales data due out later in the day and any surprises could hit the rand, though growth is expected to be healthy. The rand was at 8.7570 at 0659 GMT, up 0.4 percent from the previous day's close. It fell to a one-month low on Tuesday as the looming fiscal cliff in the U.S. ...