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	$22.89	10.197%	$25.2241	$25.22	$25.20	$25.20
Purchase #2	$66.87	11.692%	$74.6884	$74.69	$74.70	$74.70
Purchase #3	$138.76	11.399%	$154.5773	$154.58	$154.60	$154.60
Purchase #4	$104.33	7.190%	$111.8313	$111.83	$111.85	$111.80
Purchase #5	$204.82	8.519%	$222.2686	$222.27	$222.25	$222.30
Purchase #6	$249.89	11.167%	$277.7952	$277.80	$277.80	$277.80
Purchase #7	$169.69	5.182%	$178.4833	$178.48	$178.50	$178.50
7 purchase totals =	$957.25		$1,044.8682	$1,044.87	$1,044.90	$1,044.90