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	$11.27	6.709%	$12.0261	$12.03	$12.05	$12.00
Purchase #2	$128.51	11.496%	$143.2835	$143.28	$143.30	$143.30
Purchase #3	$244.27	6.655%	$260.5262	$260.53	$260.55	$260.50
Purchase #4	$233.89	11.113%	$259.8822	$259.88	$259.90	$259.90
Purchase #5	$189.77	3.302%	$196.0362	$196.04	$196.05	$196.00
Purchase #6	$62.57	6.415%	$66.5839	$66.58	$66.60	$66.60
Purchase #7	$200.43	7.857%	$216.1778	$216.18	$216.20	$216.20
7 purchase totals =	$1,070.71		$1,154.5159	$1,154.52	$1,154.65	$1,154.50