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	$52.52	6.504%	$55.9359	$55.94	$55.95	$55.90
Purchase #2	$124.96	5.706%	$132.0902	$132.09	$132.10	$132.10
Purchase #3	$179.50	11.813%	$200.7043	$200.70	$200.70	$200.70
Purchase #4	$112.88	9.362%	$123.4478	$123.45	$123.45	$123.40
Purchase #5	$185.90	12.236%	$208.6467	$208.65	$208.65	$208.60
Purchase #6	$112.48	3.464%	$116.3763	$116.38	$116.40	$116.40
Purchase #7	$44.88	8.761%	$48.8119	$48.81	$48.80	$48.80
7 purchase totals =	$813.12		$886.0131	$886.02	$886.05	$885.90