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	$246.84	4.601%	$258.1971	$258.20	$258.20	$258.20
Purchase #2	$247.25	4.409%	$258.1513	$258.15	$258.15	$258.20
Purchase #3	$55.30	6.848%	$59.0869	$59.09	$59.10	$59.10
Purchase #4	$10.73	8.327%	$11.6235	$11.62	$11.60	$11.60
Purchase #5	$51.55	7.282%	$55.3039	$55.30	$55.30	$55.30
Purchase #6	$174.45	3.759%	$181.0076	$181.01	$181.00	$181.00
Purchase #7	$160.52	11.305%	$178.6668	$178.67	$178.65	$178.70
7 purchase totals =	$946.64		$1,002.0371	$1,002.04	$1,002.00	$1,002.10