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	$177.29	9.722%	$194.5261	$194.53	$194.55	$194.50
Purchase #2	$74.83	7.497%	$80.44	$80.44	$80.45	$80.40
Purchase #3	$80.31	13.497%	$91.1494	$91.15	$91.15	$91.10
Purchase #4	$143.61	5.224%	$151.1122	$151.11	$151.10	$151.10
Purchase #5	$126.37	13.731%	$143.7219	$143.72	$143.70	$143.70
Purchase #6	$168.54	13.228%	$190.8345	$190.83	$190.85	$190.80
Purchase #7	$89.63	12.197%	$100.5622	$100.56	$100.55	$100.60
7 purchase totals =	$860.58		$952.3463	$952.34	$952.35	$952.20