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	$178.67	9.820%	$196.2154	$196.22	$196.20	$196.20
Purchase #2	$48.55	7.809%	$52.3413	$52.34	$52.35	$52.30
Purchase #3	$237.31	6.257%	$252.1585	$252.16	$252.15	$252.20
Purchase #4	$9.98	13.114%	$11.2888	$11.29	$11.30	$11.30
Purchase #5	$95.90	4.490%	$100.2059	$100.21	$100.20	$100.20
Purchase #6	$120.32	5.315%	$126.715	$126.72	$126.70	$126.70
Purchase #7	$76.27	3.400%	$78.8632	$78.86	$78.85	$78.90
7 purchase totals =	$767.00		$817.7881	$817.80	$817.75	$817.80