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	$22.70	9.547%	$24.8672	$24.87	$24.85	$24.90
Purchase #2	$156.27	11.126%	$173.6566	$173.66	$173.65	$173.70
Purchase #3	$108.54	3.556%	$112.3997	$112.40	$112.40	$112.40
Purchase #4	$243.35	11.738%	$271.9144	$271.91	$271.90	$271.90
Purchase #5	$12.37	7.386%	$13.2836	$13.28	$13.30	$13.30
Purchase #6	$240.82	9.680%	$264.1314	$264.13	$264.15	$264.10
Purchase #7	$172.85	7.302%	$185.4715	$185.47	$185.45	$185.50
7 purchase totals =	$956.90		$1,045.7244	$1,045.72	$1,045.70	$1,045.80