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	$64.93	10.602%	$71.8139	$71.81	$71.80	$71.80
Purchase #2	$44.64	4.209%	$46.5189	$46.52	$46.50	$46.50
Purchase #3	$238.57	7.184%	$255.7089	$255.71	$255.70	$255.70
Purchase #4	$209.59	6.359%	$222.9178	$222.92	$222.90	$222.90
Purchase #5	$24.39	5.523%	$25.7371	$25.74	$25.75	$25.70
Purchase #6	$36.78	13.387%	$41.7037	$41.70	$41.70	$41.70
Purchase #7	$177.35	10.744%	$196.4045	$196.40	$196.40	$196.40
7 purchase totals =	$796.25		$860.8048	$860.80	$860.75	$860.70