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	$200.81	10.285%	$221.4633	$221.46	$221.45	$221.50
Purchase #2	$180.69	10.232%	$199.1782	$199.18	$199.20	$199.20
Purchase #3	$6.52	6.360%	$6.9347	$6.93	$6.95	$6.90
Purchase #4	$199.33	11.137%	$221.5294	$221.53	$221.55	$221.50
Purchase #5	$125.75	5.695%	$132.9115	$132.91	$132.90	$132.90
Purchase #6	$214.72	8.835%	$233.6905	$233.69	$233.70	$233.70
Purchase #7	$241.76	5.692%	$255.521	$255.52	$255.50	$255.50
7 purchase totals =	$1,169.58		$1,271.2286	$1,271.22	$1,271.25	$1,271.20