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	$212.90	5.734%	$225.1077	$225.11	$225.10	$225.10
Purchase #2	$103.95	13.127%	$117.5955	$117.60	$117.60	$117.60
Purchase #3	$102.32	13.514%	$116.1475	$116.15	$116.15	$116.10
Purchase #4	$224.32	12.314%	$251.9428	$251.94	$251.95	$251.90
Purchase #5	$106.56	4.303%	$111.1453	$111.15	$111.15	$111.10
Purchase #6	$247.95	8.810%	$269.7944	$269.79	$269.80	$269.80
Purchase #7	$34.50	9.734%	$37.8582	$37.86	$37.85	$37.90
7 purchase totals =	$1,032.50		$1,129.5914	$1,129.60	$1,129.60	$1,129.50