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	$149.77	5.795%	$158.4492	$158.45	$158.45	$158.40
Purchase #2	$81.70	10.435%	$90.2254	$90.23	$90.25	$90.20
Purchase #3	$53.61	8.394%	$58.11	$58.11	$58.10	$58.10
Purchase #4	$23.55	9.824%	$25.8636	$25.86	$25.85	$25.90
Purchase #5	$147.78	12.840%	$166.755	$166.76	$166.75	$166.80
Purchase #6	$105.66	5.519%	$111.4914	$111.49	$111.50	$111.50
Purchase #7	$139.98	4.175%	$145.8242	$145.82	$145.80	$145.80
7 purchase totals =	$702.05		$756.7188	$756.72	$756.70	$756.70