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	$101.72	6.456%	$108.287	$108.29	$108.30	$108.30
Purchase #2	$77.39	10.511%	$85.5245	$85.52	$85.50	$85.50
Purchase #3	$176.75	4.381%	$184.4934	$184.49	$184.50	$184.50
Purchase #4	$83.50	4.837%	$87.5389	$87.54	$87.55	$87.50
Purchase #5	$127.72	3.125%	$131.7113	$131.71	$131.70	$131.70
Purchase #6	$225.96	4.826%	$236.8648	$236.86	$236.85	$236.90
Purchase #7	$53.54	12.621%	$60.2973	$60.30	$60.30	$60.30
7 purchase totals =	$846.58		$894.7172	$894.71	$894.70	$894.70