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	$178.43	12.306%	$200.3876	$200.39	$200.40	$200.40
Purchase #2	$145.63	13.577%	$165.4022	$165.40	$165.40	$165.40
Purchase #3	$139.51	8.291%	$151.0768	$151.08	$151.10	$151.10
Purchase #4	$247.43	13.427%	$280.6524	$280.65	$280.65	$280.70
Purchase #5	$83.94	8.295%	$90.9028	$90.90	$90.90	$90.90
Purchase #6	$49.60	11.838%	$55.4716	$55.47	$55.45	$55.50
Purchase #7	$234.60	6.721%	$250.3675	$250.37	$250.35	$250.40
7 purchase totals =	$1,079.14		$1,194.2609	$1,194.26	$1,194.25	$1,194.40