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	$167.39	6.129%	$177.6493	$177.65	$177.65	$177.60
Purchase #2	$11.85	12.605%	$13.3437	$13.34	$13.35	$13.30
Purchase #3	$102.33	5.593%	$108.0533	$108.05	$108.05	$108.10
Purchase #4	$176.77	7.814%	$190.5828	$190.58	$190.60	$190.60
Purchase #5	$195.82	9.538%	$214.4973	$214.50	$214.50	$214.50
Purchase #6	$19.53	3.108%	$20.137	$20.14	$20.15	$20.10
Purchase #7	$81.84	10.705%	$90.601	$90.60	$90.60	$90.60
7 purchase totals =	$755.53		$814.8644	$814.86	$814.90	$814.80