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	$193.80	13.824%	$220.5909	$220.59	$220.60	$220.60
Purchase #2	$67.27	13.570%	$76.3985	$76.40	$76.40	$76.40
Purchase #3	$19.83	3.498%	$20.5237	$20.52	$20.50	$20.50
Purchase #4	$48.26	5.189%	$50.7642	$50.76	$50.75	$50.80
Purchase #5	$6.53	13.509%	$7.4121	$7.41	$7.40	$7.40
Purchase #6	$232.25	5.346%	$244.6661	$244.67	$244.65	$244.70
Purchase #7	$104.62	6.187%	$111.0928	$111.09	$111.10	$111.10
7 purchase totals =	$672.56		$731.4483	$731.44	$731.40	$731.50