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	$82.27	4.301%	$85.8084	$85.81	$85.80	$85.80
Purchase #2	$26.47	10.255%	$29.1845	$29.18	$29.20	$29.20
Purchase #3	$125.39	11.606%	$139.9428	$139.94	$139.95	$139.90
Purchase #4	$107.37	11.323%	$119.5275	$119.53	$119.55	$119.50
Purchase #5	$197.48	8.703%	$214.6667	$214.67	$214.65	$214.70
Purchase #6	$98.89	12.727%	$111.4757	$111.48	$111.50	$111.50
Purchase #7	$22.31	11.533%	$24.883	$24.88	$24.90	$24.90
7 purchase totals =	$660.18		$725.4886	$725.49	$725.55	$725.50