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	$56.48	4.576%	$59.0645	$59.06	$59.05	$59.10
Purchase #2	$148.84	13.718%	$169.2579	$169.26	$169.25	$169.30
Purchase #3	$230.46	12.537%	$259.3528	$259.35	$259.35	$259.40
Purchase #4	$50.27	4.655%	$52.6101	$52.61	$52.60	$52.60
Purchase #5	$190.81	4.816%	$199.9994	$200.00	$200.00	$200.00
Purchase #6	$105.99	6.559%	$112.9419	$112.94	$112.95	$112.90
Purchase #7	$101.44	10.870%	$112.4665	$112.47	$112.45	$112.50
7 purchase totals =	$884.29		$965.6931	$965.69	$965.65	$965.80