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	$136.48	6.710%	$145.6378	$145.64	$145.65	$145.60
Purchase #2	$227.43	6.361%	$241.8968	$241.90	$241.90	$241.90
Purchase #3	$55.38	12.766%	$62.4498	$62.45	$62.45	$62.40
Purchase #4	$247.48	7.117%	$265.0932	$265.09	$265.10	$265.10
Purchase #5	$43.72	5.279%	$46.028	$46.03	$46.05	$46.00
Purchase #6	$139.46	13.681%	$158.5395	$158.54	$158.55	$158.50
Purchase #7	$21.57	12.616%	$24.2913	$24.29	$24.30	$24.30
7 purchase totals =	$871.52		$943.9364	$943.94	$944.00	$943.80