"Everybody knows it's not a saving. We don't intentionally put 1c savings out there. It can range from anything to human error to a system issue. We appreciate people bringing them to our attention."
Mr Donohue said the supermarket had offered savings in excess of A$500 million (NZ$520m) through lower prices in the past 12 months. "Forget about 1c, look at the bottom of the docket when you shop," he said.
There has been sharp discounting by the nation's two biggest supermarkets, which are promising shoppers the cheapest Christmas in five years.
Last week, Coles managing director John Durkan said he believed the supermarket was well in front "on the products that we've found matter most to customers at this time of year".
"Coles is committed to making this the best value Christmas in years," Mr Durkan said. "We know our customers have long shopping lists this month, so it's more important than ever that we deliver great value across our stores."
Coles calculated that, excluding specials, it beat its rival on a basket of 29 Christmas items including leg ham, fruit mince pies, frozen turkey and panettone, with a bill of A$155.89 (NZ$155.89) at Coles and A$169.53 (NZ$176.41) at Woolworths.
Mr Donohue countered that the supermarket was "confident we're delivering the best value, quality and service for our customers this Christmas", with cheaper prices on special items such as Roses chocolates.
"Christmas has been really strong so far, we're finding that there have been certain categories selling well ahead of the same time last year," he said. "The pav is well and truly back this year. We lowered our pavlovas to A$8 (NZ$8.32) and have experienced record sales.
"We're selling out of mince pies, and in the last few days our team have shucked almost one million oysters. Prawns have been a big hit, and we've seen outstanding demand for our Christmas hams. Then there's the usual stuff like turkeys and pork, which will really start to take off from now to Christmas."
Woolworths currently has 36.3 per cent market share of Australia's A$90 billion (NZ$93b) grocery market, according to Roy Morgan, with Coles on 33.2 per cent. Discount chain Aldi now holds 12.5 per cent, and analysts believe will reach 15 per cent in the near future.
A recent Morgan Stanley report suggested Woolworths' turnaround strategy was beginning to eat into Coles' sales growth. "Woolworths' like-for-like sales growth now appears to be ahead of Coles," wrote Morgan Stanley analyst Thomas Kierath. "This would be a first since the first quarter of 2010."
In October, Woolworths posted its first quarterly sales growth in almost a year, with comparable sales up 0.7 per cent, beating analysts' expectations.
