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	$90.42	11.275%	$100.6149	$100.61	$100.60	$100.60
Purchase #2	$32.70	6.179%	$34.7205	$34.72	$34.70	$34.70
Purchase #3	$207.29	4.822%	$217.2855	$217.29	$217.30	$217.30
Purchase #4	$189.82	3.419%	$196.3099	$196.31	$196.30	$196.30
Purchase #5	$46.46	5.549%	$49.0381	$49.04	$49.05	$49.00
Purchase #6	$222.76	13.137%	$252.024	$252.02	$252.00	$252.00
Purchase #7	$132.55	5.446%	$139.7687	$139.77	$139.75	$139.80
7 purchase totals =	$922.00		$989.7616	$989.76	$989.70	$989.70