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	$243.48	13.448%	$276.2232	$276.22	$276.20	$276.20
Purchase #2	$107.51	6.752%	$114.7691	$114.77	$114.75	$114.80
Purchase #3	$59.48	5.592%	$62.8061	$62.81	$62.80	$62.80
Purchase #4	$228.88	7.672%	$246.4397	$246.44	$246.45	$246.40
Purchase #5	$101.25	7.306%	$108.6473	$108.65	$108.65	$108.60
Purchase #6	$155.41	3.741%	$161.2239	$161.22	$161.20	$161.20
Purchase #7	$100.93	10.859%	$111.89	$111.89	$111.90	$111.90
7 purchase totals =	$996.94		$1,081.9993	$1,082.00	$1,081.95	$1,081.90