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	$239.65	11.687%	$267.6579	$267.66	$267.65	$267.70
Purchase #2	$100.89	10.834%	$111.8204	$111.82	$111.80	$111.80
Purchase #3	$20.36	6.693%	$21.7227	$21.72	$21.70	$21.70
Purchase #4	$114.54	5.258%	$120.5625	$120.56	$120.55	$120.60
Purchase #5	$120.58	4.677%	$126.2195	$126.22	$126.20	$126.20
Purchase #6	$184.88	6.417%	$196.7437	$196.74	$196.75	$196.70
Purchase #7	$47.31	6.613%	$50.4386	$50.44	$50.45	$50.40
7 purchase totals =	$828.21		$895.1653	$895.16	$895.10	$895.10