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	$95.75	13.679%	$108.8476	$108.85	$108.85	$108.80
Purchase #2	$21.75	9.791%	$23.8795	$23.88	$23.90	$23.90
Purchase #3	$114.41	7.164%	$122.6063	$122.61	$122.60	$122.60
Purchase #4	$74.56	11.373%	$83.0397	$83.04	$83.05	$83.00
Purchase #5	$171.88	8.458%	$186.4176	$186.42	$186.40	$186.40
Purchase #6	$223.64	13.653%	$254.1736	$254.17	$254.15	$254.20
Purchase #7	$99.47	11.862%	$111.2691	$111.27	$111.25	$111.30
7 purchase totals =	$801.46		$890.2334	$890.24	$890.20	$890.20