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	$193.89	5.430%	$204.4182	$204.42	$204.40	$204.40
Purchase #2	$37.29	9.193%	$40.7181	$40.72	$40.70	$40.70
Purchase #3	$202.95	11.276%	$225.8346	$225.83	$225.85	$225.80
Purchase #4	$48.25	6.165%	$51.2246	$51.22	$51.20	$51.20
Purchase #5	$95.31	3.794%	$98.9261	$98.93	$98.95	$98.90
Purchase #6	$59.66	6.587%	$63.5898	$63.59	$63.60	$63.60
Purchase #7	$29.83	13.162%	$33.7562	$33.76	$33.75	$33.80
7 purchase totals =	$667.18		$718.4676	$718.47	$718.45	$718.40