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	$117.35	8.554%	$127.3881	$127.39	$127.40	$127.40
Purchase #2	$82.48	7.694%	$88.826	$88.83	$88.85	$88.80
Purchase #3	$95.52	4.605%	$99.9187	$99.92	$99.90	$99.90
Purchase #4	$241.59	8.408%	$261.9029	$261.90	$261.90	$261.90
Purchase #5	$210.38	5.564%	$222.0855	$222.09	$222.10	$222.10
Purchase #6	$27.48	3.363%	$28.4042	$28.40	$28.40	$28.40
Purchase #7	$36.78	3.833%	$38.1898	$38.19	$38.20	$38.20
7 purchase totals =	$811.58		$866.7152	$866.72	$866.75	$866.70