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	$32.71	4.870%	$34.303	$34.30	$34.30	$34.30
Purchase #2	$183.51	5.536%	$193.6691	$193.67	$193.65	$193.70
Purchase #3	$206.78	4.599%	$216.2898	$216.29	$216.30	$216.30
Purchase #4	$130.88	6.742%	$139.7039	$139.70	$139.70	$139.70
Purchase #5	$158.52	4.131%	$165.0685	$165.07	$165.05	$165.10
Purchase #6	$104.64	6.544%	$111.4876	$111.49	$111.50	$111.50
Purchase #7	$47.41	13.527%	$53.8232	$53.82	$53.80	$53.80
7 purchase totals =	$864.45		$914.3451	$914.34	$914.30	$914.40