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	$81.60	10.477%	$90.1492	$90.15	$90.15	$90.10
Purchase #2	$179.33	8.657%	$194.8546	$194.85	$194.85	$194.90
Purchase #3	$50.60	11.676%	$56.5081	$56.51	$56.50	$56.50
Purchase #4	$133.72	12.340%	$150.221	$150.22	$150.20	$150.20
Purchase #5	$198.58	11.764%	$221.941	$221.94	$221.95	$221.90
Purchase #6	$219.47	5.148%	$230.7683	$230.77	$230.75	$230.80
Purchase #7	$111.76	4.650%	$116.9568	$116.96	$116.95	$117.00
7 purchase totals =	$975.06		$1,061.3990	$1,061.40	$1,061.35	$1,061.40