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	$210.95	10.221%	$232.5112	$232.51	$232.50	$232.50
Purchase #2	$33.77	10.648%	$37.3658	$37.37	$37.35	$37.40
Purchase #3	$117.84	10.590%	$130.3193	$130.32	$130.30	$130.30
Purchase #4	$225.82	6.244%	$239.9202	$239.92	$239.90	$239.90
Purchase #5	$52.59	13.164%	$59.5129	$59.51	$59.50	$59.50
Purchase #6	$55.37	3.727%	$57.4336	$57.43	$57.45	$57.40
Purchase #7	$45.96	5.208%	$48.3536	$48.35	$48.35	$48.40
7 purchase totals =	$742.30		$805.4166	$805.41	$805.35	$805.40