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	$201.30	13.536%	$228.548	$228.55	$228.55	$228.50
Purchase #2	$103.54	7.235%	$111.0311	$111.03	$111.05	$111.00
Purchase #3	$210.84	6.222%	$223.9585	$223.96	$223.95	$224.00
Purchase #4	$183.41	6.336%	$195.0309	$195.03	$195.05	$195.00
Purchase #5	$39.39	8.609%	$42.7811	$42.78	$42.80	$42.80
Purchase #6	$140.27	13.153%	$158.7197	$158.72	$158.70	$158.70
Purchase #7	$165.27	4.128%	$172.0923	$172.09	$172.10	$172.10
7 purchase totals =	$1,044.02		$1,132.1616	$1,132.16	$1,132.20	$1,132.10