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	$237.47	9.427%	$259.8563	$259.86	$259.85	$259.90
Purchase #2	$95.67	10.602%	$105.8129	$105.81	$105.80	$105.80
Purchase #3	$132.53	6.413%	$141.0291	$141.03	$141.05	$141.00
Purchase #4	$161.40	7.149%	$172.9385	$172.94	$172.95	$172.90
Purchase #5	$69.85	10.670%	$77.303	$77.30	$77.30	$77.30
Purchase #6	$238.70	3.639%	$247.3863	$247.39	$247.40	$247.40
Purchase #7	$174.90	6.788%	$186.7722	$186.77	$186.75	$186.80
7 purchase totals =	$1,110.52		$1,191.0983	$1,191.10	$1,191.10	$1,191.10