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	$63.37	13.176%	$71.7196	$71.72	$71.70	$71.70
Purchase #2	$52.57	3.538%	$54.4299	$54.43	$54.45	$54.40
Purchase #3	$121.67	8.423%	$131.9183	$131.92	$131.90	$131.90
Purchase #4	$120.98	6.323%	$128.6296	$128.63	$128.65	$128.60
Purchase #5	$122.30	3.451%	$126.5206	$126.52	$126.50	$126.50
Purchase #6	$193.72	11.719%	$216.422	$216.42	$216.40	$216.40
Purchase #7	$36.65	9.670%	$40.1941	$40.19	$40.20	$40.20
7 purchase totals =	$711.26		$769.8341	$769.83	$769.80	$769.70