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	$51.56	13.770%	$58.6598	$58.66	$58.65	$58.70
Purchase #2	$196.40	13.470%	$222.8551	$222.86	$222.85	$222.90
Purchase #3	$95.83	11.803%	$107.1408	$107.14	$107.15	$107.10
Purchase #4	$44.31	8.581%	$48.1122	$48.11	$48.10	$48.10
Purchase #5	$112.35	7.161%	$120.3954	$120.40	$120.40	$120.40
Purchase #6	$106.53	4.688%	$111.5241	$111.52	$111.50	$111.50
Purchase #7	$159.80	10.261%	$176.1971	$176.20	$176.20	$176.20
7 purchase totals =	$766.78		$844.8845	$844.89	$844.85	$844.90