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	$208.99	11.874%	$233.8055	$233.81	$233.80	$233.80
Purchase #2	$187.52	5.801%	$198.398	$198.40	$198.40	$198.40
Purchase #3	$95.62	5.511%	$100.8896	$100.89	$100.90	$100.90
Purchase #4	$16.89	7.189%	$18.1042	$18.10	$18.10	$18.10
Purchase #5	$30.66	10.462%	$33.8676	$33.87	$33.85	$33.90
Purchase #6	$95.76	6.349%	$101.8398	$101.84	$101.85	$101.80
Purchase #7	$247.82	11.350%	$275.9476	$275.95	$275.95	$275.90
7 purchase totals =	$883.26		$962.8523	$962.86	$962.85	$962.80