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	$227.96	12.592%	$256.6647	$256.66	$256.65	$256.70
Purchase #2	$147.59	5.856%	$156.2329	$156.23	$156.25	$156.20
Purchase #3	$122.53	3.158%	$126.3995	$126.40	$126.40	$126.40
Purchase #4	$60.54	11.678%	$67.6099	$67.61	$67.60	$67.60
Purchase #5	$177.47	11.558%	$197.982	$197.98	$198.00	$198.00
Purchase #6	$175.61	4.573%	$183.6406	$183.64	$183.65	$183.60
Purchase #7	$50.82	4.283%	$52.9966	$53.00	$53.00	$53.00
7 purchase totals =	$962.52		$1,041.5262	$1,041.52	$1,041.55	$1,041.50