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	$114.51	8.607%	$124.3659	$124.37	$124.35	$124.40
Purchase #2	$227.60	12.339%	$255.6836	$255.68	$255.70	$255.70
Purchase #3	$49.55	6.109%	$52.577	$52.58	$52.60	$52.60
Purchase #4	$138.30	12.726%	$155.9001	$155.90	$155.90	$155.90
Purchase #5	$175.86	13.311%	$199.2687	$199.27	$199.25	$199.30
Purchase #6	$87.86	13.192%	$99.4505	$99.45	$99.45	$99.50
Purchase #7	$223.50	5.529%	$235.8573	$235.86	$235.85	$235.90
7 purchase totals =	$1,017.18		$1,123.1031	$1,123.11	$1,123.10	$1,123.30