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	$223.54	4.509%	$233.6194	$233.62	$233.60	$233.60
Purchase #2	$119.87	8.841%	$130.4677	$130.47	$130.45	$130.50
Purchase #3	$208.60	6.122%	$221.3705	$221.37	$221.35	$221.40
Purchase #4	$240.48	5.233%	$253.0643	$253.06	$253.05	$253.10
Purchase #5	$77.64	10.160%	$85.5282	$85.53	$85.55	$85.50
Purchase #6	$55.27	13.253%	$62.5949	$62.59	$62.60	$62.60
Purchase #7	$235.30	3.306%	$243.079	$243.08	$243.10	$243.10
7 purchase totals =	$1,160.70		$1,229.7240	$1,229.72	$1,229.70	$1,229.80