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	$85.60	6.677%	$91.3155	$91.32	$91.30	$91.30
Purchase #2	$176.53	11.424%	$196.6968	$196.70	$196.70	$196.70
Purchase #3	$131.75	6.675%	$140.5443	$140.54	$140.55	$140.50
Purchase #4	$249.98	13.514%	$283.7623	$283.76	$283.75	$283.80
Purchase #5	$154.31	13.763%	$175.5477	$175.55	$175.55	$175.50
Purchase #6	$48.92	3.353%	$50.5603	$50.56	$50.55	$50.60
Purchase #7	$200.85	5.594%	$212.0855	$212.09	$212.10	$212.10
7 purchase totals =	$1,047.94		$1,150.5124	$1,150.52	$1,150.50	$1,150.50