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	$214.49	3.286%	$221.5381	$221.54	$221.55	$221.50
Purchase #2	$98.77	10.204%	$108.8485	$108.85	$108.85	$108.80
Purchase #3	$53.51	12.840%	$60.3807	$60.38	$60.40	$60.40
Purchase #4	$96.42	3.539%	$99.8323	$99.83	$99.85	$99.80
Purchase #5	$169.89	12.103%	$190.4518	$190.45	$190.45	$190.50
Purchase #6	$14.61	11.374%	$16.2717	$16.27	$16.25	$16.30
Purchase #7	$111.77	6.563%	$119.1055	$119.11	$119.10	$119.10
7 purchase totals =	$759.46		$816.4286	$816.43	$816.45	$816.40