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	$227.32	12.278%	$255.2303	$255.23	$255.25	$255.20
Purchase #2	$214.43	4.413%	$223.8928	$223.89	$223.90	$223.90
Purchase #3	$40.57	3.233%	$41.8816	$41.88	$41.90	$41.90
Purchase #4	$54.34	13.643%	$61.7536	$61.75	$61.75	$61.80
Purchase #5	$158.37	8.786%	$172.2844	$172.28	$172.30	$172.30
Purchase #6	$229.78	11.283%	$255.7061	$255.71	$255.70	$255.70
Purchase #7	$177.42	10.781%	$196.5477	$196.55	$196.55	$196.50
7 purchase totals =	$1,102.23		$1,207.2965	$1,207.29	$1,207.35	$1,207.30