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	$108.77	13.846%	$123.8303	$123.83	$123.85	$123.80
Purchase #2	$145.27	3.579%	$150.4692	$150.47	$150.45	$150.50
Purchase #3	$223.93	10.113%	$246.576	$246.58	$246.60	$246.60
Purchase #4	$29.76	13.141%	$33.6708	$33.67	$33.65	$33.70
Purchase #5	$9.67	7.671%	$10.4118	$10.41	$10.40	$10.40
Purchase #6	$89.86	6.342%	$95.5589	$95.56	$95.55	$95.60
Purchase #7	$221.96	4.389%	$231.7018	$231.70	$231.70	$231.70
7 purchase totals =	$829.22		$892.2188	$892.22	$892.20	$892.30