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	$145.51	3.583%	$150.7236	$150.72	$150.70	$150.70
Purchase #2	$50.40	4.721%	$52.7794	$52.78	$52.80	$52.80
Purchase #3	$37.71	11.562%	$42.07	$42.07	$42.05	$42.10
Purchase #4	$236.49	11.386%	$263.4168	$263.42	$263.40	$263.40
Purchase #5	$41.30	8.365%	$44.7547	$44.75	$44.75	$44.80
Purchase #6	$65.54	3.517%	$67.845	$67.85	$67.85	$67.80
Purchase #7	$234.43	5.198%	$246.6157	$246.62	$246.60	$246.60
7 purchase totals =	$811.38		$868.2052	$868.21	$868.15	$868.20