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	$178.60	3.105%	$184.1455	$184.15	$184.15	$184.10
Purchase #2	$5.64	11.573%	$6.2927	$6.29	$6.30	$6.30
Purchase #3	$242.50	5.497%	$255.8302	$255.83	$255.85	$255.80
Purchase #4	$174.40	10.814%	$193.2596	$193.26	$193.25	$193.30
Purchase #5	$236.32	4.455%	$246.8481	$246.85	$246.85	$246.80
Purchase #6	$9.72	5.468%	$10.2515	$10.25	$10.25	$10.30
Purchase #7	$62.88	13.848%	$71.5876	$71.59	$71.60	$71.60
7 purchase totals =	$910.06		$968.2152	$968.22	$968.25	$968.20