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	$221.83	6.763%	$236.8324	$236.83	$236.85	$236.80
Purchase #2	$67.82	10.424%	$74.8896	$74.89	$74.90	$74.90
Purchase #3	$132.76	12.162%	$148.9063	$148.91	$148.90	$148.90
Purchase #4	$55.65	8.827%	$60.5622	$60.56	$60.55	$60.60
Purchase #5	$115.82	10.433%	$127.9035	$127.90	$127.90	$127.90
Purchase #6	$191.51	4.519%	$200.1643	$200.16	$200.15	$200.20
Purchase #7	$239.27	3.500%	$247.6445	$247.64	$247.65	$247.60
7 purchase totals =	$1,024.66		$1,096.9028	$1,096.89	$1,096.90	$1,096.90