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	$166.47	3.417%	$172.1583	$172.16	$172.15	$172.20
Purchase #2	$227.45	13.382%	$257.8874	$257.89	$257.90	$257.90
Purchase #3	$139.75	6.213%	$148.4327	$148.43	$148.45	$148.40
Purchase #4	$123.43	5.863%	$130.6667	$130.67	$130.65	$130.70
Purchase #5	$84.50	9.517%	$92.5419	$92.54	$92.55	$92.50
Purchase #6	$89.71	6.678%	$95.7008	$95.70	$95.70	$95.70
Purchase #7	$245.88	4.732%	$257.515	$257.52	$257.50	$257.50
7 purchase totals =	$1,077.19		$1,154.9028	$1,154.91	$1,154.90	$1,154.90