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	$249.51	6.246%	$265.0944	$265.09	$265.10	$265.10
Purchase #2	$92.92	8.333%	$100.663	$100.66	$100.65	$100.70
Purchase #3	$56.66	4.466%	$59.1904	$59.19	$59.20	$59.20
Purchase #4	$68.67	11.206%	$76.3652	$76.37	$76.35	$76.40
Purchase #5	$133.54	7.617%	$143.7117	$143.71	$143.70	$143.70
Purchase #6	$64.90	3.737%	$67.3253	$67.33	$67.35	$67.30
Purchase #7	$215.68	12.163%	$241.9132	$241.91	$241.90	$241.90
7 purchase totals =	$881.88		$954.2632	$954.26	$954.25	$954.30