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	$123.36	4.840%	$129.3306	$129.33	$129.35	$129.30
Purchase #2	$60.63	8.529%	$65.8011	$65.80	$65.80	$65.80
Purchase #3	$97.37	6.699%	$103.8928	$103.89	$103.90	$103.90
Purchase #4	$95.53	4.810%	$100.125	$100.13	$100.15	$100.10
Purchase #5	$11.32	11.318%	$12.6012	$12.60	$12.60	$12.60
Purchase #6	$100.62	10.611%	$111.2968	$111.30	$111.30	$111.30
Purchase #7	$220.32	9.343%	$240.9045	$240.90	$240.90	$240.90
7 purchase totals =	$709.15		$763.9520	$763.95	$764.00	$763.90