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	$117.87	12.528%	$132.6368	$132.64	$132.65	$132.60
Purchase #2	$44.93	12.628%	$50.6038	$50.60	$50.60	$50.60
Purchase #3	$11.44	6.276%	$12.158	$12.16	$12.15	$12.20
Purchase #4	$85.90	4.758%	$89.9871	$89.99	$90.00	$90.00
Purchase #5	$234.33	13.709%	$266.4543	$266.45	$266.45	$266.50
Purchase #6	$239.70	6.583%	$255.4795	$255.48	$255.50	$255.50
Purchase #7	$70.67	11.585%	$78.8571	$78.86	$78.85	$78.90
7 purchase totals =	$804.84		$886.1766	$886.18	$886.20	$886.30