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	$160.96	4.124%	$167.598	$167.60	$167.60	$167.60
Purchase #2	$145.75	5.328%	$153.5156	$153.52	$153.50	$153.50
Purchase #3	$143.64	6.512%	$152.9938	$152.99	$153.00	$153.00
Purchase #4	$95.72	3.797%	$99.3545	$99.35	$99.35	$99.40
Purchase #5	$39.39	4.580%	$41.1941	$41.19	$41.20	$41.20
Purchase #6	$182.59	4.177%	$190.2168	$190.22	$190.20	$190.20
Purchase #7	$198.70	13.548%	$225.6199	$225.62	$225.60	$225.60
7 purchase totals =	$966.75		$1,030.4927	$1,030.49	$1,030.45	$1,030.50