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	$153.75	13.402%	$174.3556	$174.36	$174.35	$174.40
Purchase #2	$23.25	10.643%	$25.7245	$25.72	$25.70	$25.70
Purchase #3	$239.47	7.160%	$256.6161	$256.62	$256.60	$256.60
Purchase #4	$155.39	3.204%	$160.3687	$160.37	$160.35	$160.40
Purchase #5	$94.98	5.354%	$100.0652	$100.07	$100.05	$100.10
Purchase #6	$55.86	11.329%	$62.1884	$62.19	$62.20	$62.20
Purchase #7	$83.32	7.613%	$89.6632	$89.66	$89.65	$89.70
7 purchase totals =	$806.02		$868.9817	$868.99	$868.90	$869.10