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	$185.84	7.675%	$200.1032	$200.10	$200.10	$200.10
Purchase #2	$184.41	10.562%	$203.8874	$203.89	$203.90	$203.90
Purchase #3	$28.66	3.797%	$29.7482	$29.75	$29.75	$29.70
Purchase #4	$173.67	13.208%	$196.6083	$196.61	$196.60	$196.60
Purchase #5	$44.83	4.599%	$46.8917	$46.89	$46.90	$46.90
Purchase #6	$59.27	12.282%	$66.5495	$66.55	$66.55	$66.50
Purchase #7	$146.36	8.197%	$158.3571	$158.36	$158.35	$158.40
7 purchase totals =	$823.04		$902.1454	$902.15	$902.15	$902.10