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	$246.72	6.581%	$262.9566	$262.96	$262.95	$263.00
Purchase #2	$60.78	11.559%	$67.8056	$67.81	$67.80	$67.80
Purchase #3	$105.60	4.610%	$110.4682	$110.47	$110.45	$110.50
Purchase #4	$107.75	10.531%	$119.0972	$119.10	$119.10	$119.10
Purchase #5	$69.53	12.559%	$78.2623	$78.26	$78.25	$78.30
Purchase #6	$80.80	3.436%	$83.5763	$83.58	$83.60	$83.60
Purchase #7	$114.96	13.416%	$130.383	$130.38	$130.40	$130.40
7 purchase totals =	$786.14		$852.5492	$852.56	$852.55	$852.70