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	$145.78	3.490%	$150.8677	$150.87	$150.85	$150.90
Purchase #2	$61.62	7.419%	$66.1916	$66.19	$66.20	$66.20
Purchase #3	$127.85	6.441%	$136.0848	$136.08	$136.10	$136.10
Purchase #4	$190.74	10.496%	$210.7601	$210.76	$210.75	$210.80
Purchase #5	$250.47	11.655%	$279.6623	$279.66	$279.65	$279.70
Purchase #6	$74.67	10.176%	$82.2684	$82.27	$82.25	$82.30
Purchase #7	$141.32	5.149%	$148.5966	$148.60	$148.60	$148.60
7 purchase totals =	$992.45		$1,074.4315	$1,074.43	$1,074.40	$1,074.60