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	$181.47	8.466%	$196.8333	$196.83	$196.85	$196.80
Purchase #2	$37.54	3.415%	$38.822	$38.82	$38.80	$38.80
Purchase #3	$49.72	4.758%	$52.0857	$52.09	$52.10	$52.10
Purchase #4	$36.92	10.188%	$40.6814	$40.68	$40.70	$40.70
Purchase #5	$21.65	6.776%	$23.117	$23.12	$23.10	$23.10
Purchase #6	$170.29	6.203%	$180.8531	$180.85	$180.85	$180.90
Purchase #7	$124.62	12.500%	$140.1975	$140.20	$140.20	$140.20
7 purchase totals =	$622.21		$672.5900	$672.59	$672.60	$672.60