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	$171.72	11.126%	$190.8256	$190.83	$190.85	$190.80
Purchase #2	$81.43	8.864%	$88.648	$88.65	$88.65	$88.60
Purchase #3	$55.55	6.656%	$59.2474	$59.25	$59.25	$59.20
Purchase #4	$59.89	7.657%	$64.4758	$64.48	$64.50	$64.50
Purchase #5	$87.61	10.113%	$96.47	$96.47	$96.45	$96.50
Purchase #6	$81.45	3.566%	$84.3545	$84.35	$84.35	$84.40
Purchase #7	$56.29	6.704%	$60.0637	$60.06	$60.05	$60.10
7 purchase totals =	$593.94		$644.0850	$644.09	$644.10	$644.10