Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$231.40	13.406%	$262.4215	$262.42	$262.40	$262.40
Purchase #2	$133.90	6.421%	$142.4977	$142.50	$142.50	$142.50
Purchase #3	$27.78	8.639%	$30.1799	$30.18	$30.20	$30.20
Purchase #4	$250.35	7.501%	$269.1288	$269.13	$269.15	$269.10
Purchase #5	$178.51	5.105%	$187.6229	$187.62	$187.60	$187.60
Purchase #6	$106.68	4.136%	$111.0923	$111.09	$111.10	$111.10
Purchase #7	$12.74	9.216%	$13.9141	$13.91	$13.90	$13.90
7 purchase totals =	$941.36		$1,016.8572	$1,016.85	$1,016.85	$1,016.80