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	$142.34	6.160%	$151.1081	$151.11	$151.10	$151.10
Purchase #2	$78.94	11.758%	$88.2218	$88.22	$88.20	$88.20
Purchase #3	$204.58	8.160%	$221.2737	$221.27	$221.25	$221.30
Purchase #4	$203.53	4.405%	$212.4955	$212.50	$212.50	$212.50
Purchase #5	$71.46	10.203%	$78.7511	$78.75	$78.75	$78.80
Purchase #6	$86.60	3.509%	$89.6388	$89.64	$89.65	$89.60
Purchase #7	$26.89	4.849%	$28.1939	$28.19	$28.20	$28.20
7 purchase totals =	$814.34		$869.6829	$869.68	$869.65	$869.70