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	$132.53	9.648%	$145.3165	$145.32	$145.30	$145.30
Purchase #2	$228.55	11.723%	$255.3429	$255.34	$255.35	$255.30
Purchase #3	$65.74	7.599%	$70.7356	$70.74	$70.75	$70.70
Purchase #4	$101.35	4.249%	$105.6564	$105.66	$105.65	$105.70
Purchase #5	$247.78	3.386%	$256.1698	$256.17	$256.15	$256.20
Purchase #6	$144.85	9.713%	$158.9193	$158.92	$158.90	$158.90
Purchase #7	$58.78	3.481%	$60.8261	$60.83	$60.85	$60.80
7 purchase totals =	$979.58		$1,052.9666	$1,052.98	$1,052.95	$1,052.90