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	$116.86	6.821%	$124.831	$124.83	$124.85	$124.80
Purchase #2	$44.52	6.719%	$47.5113	$47.51	$47.50	$47.50
Purchase #3	$63.30	12.177%	$71.008	$71.01	$71.00	$71.00
Purchase #4	$60.43	11.327%	$67.2749	$67.27	$67.25	$67.30
Purchase #5	$143.45	10.470%	$158.4692	$158.47	$158.45	$158.50
Purchase #6	$80.52	12.350%	$90.4642	$90.46	$90.45	$90.50
Purchase #7	$43.75	8.493%	$47.4657	$47.47	$47.45	$47.50
7 purchase totals =	$552.83		$607.0243	$607.02	$606.95	$607.10