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	$180.31	5.246%	$189.7691	$189.77	$189.75	$189.80
Purchase #2	$10.45	13.380%	$11.8482	$11.85	$11.85	$11.80
Purchase #3	$241.92	4.739%	$253.3846	$253.38	$253.40	$253.40
Purchase #4	$236.44	13.371%	$268.0544	$268.05	$268.05	$268.10
Purchase #5	$212.46	12.635%	$239.3043	$239.30	$239.30	$239.30
Purchase #6	$59.45	10.855%	$65.9033	$65.90	$65.90	$65.90
Purchase #7	$84.81	12.776%	$95.6453	$95.65	$95.65	$95.60
7 purchase totals =	$1,025.84		$1,123.9092	$1,123.90	$1,123.90	$1,123.90