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	$7.76	9.365%	$8.4867	$8.49	$8.50	$8.50
Purchase #2	$57.64	3.768%	$59.8119	$59.81	$59.80	$59.80
Purchase #3	$23.70	3.384%	$24.502	$24.50	$24.50	$24.50
Purchase #4	$143.95	5.291%	$151.5664	$151.57	$151.55	$151.60
Purchase #5	$208.31	12.464%	$234.2738	$234.27	$234.25	$234.30
Purchase #6	$10.56	11.542%	$11.7788	$11.78	$11.80	$11.80
Purchase #7	$217.40	7.852%	$234.4702	$234.47	$234.45	$234.50
7 purchase totals =	$669.32		$724.8898	$724.89	$724.85	$725.00