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	$142.83	6.523%	$152.1468	$152.15	$152.15	$152.10
Purchase #2	$203.63	7.185%	$218.2608	$218.26	$218.25	$218.30
Purchase #3	$226.70	10.506%	$250.5171	$250.52	$250.50	$250.50
Purchase #4	$199.70	9.452%	$218.5756	$218.58	$218.60	$218.60
Purchase #5	$233.40	9.323%	$255.1599	$255.16	$255.15	$255.20
Purchase #6	$140.76	10.631%	$155.7242	$155.72	$155.70	$155.70
Purchase #7	$230.43	12.350%	$258.8881	$258.89	$258.90	$258.90
7 purchase totals =	$1,377.45		$1,509.2725	$1,509.28	$1,509.25	$1,509.30