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	$216.80	6.756%	$231.447	$231.45	$231.45	$231.40
Purchase #2	$102.64	10.158%	$113.0662	$113.07	$113.05	$113.10
Purchase #3	$47.48	7.232%	$50.9138	$50.91	$50.90	$50.90
Purchase #4	$87.78	8.705%	$95.4212	$95.42	$95.40	$95.40
Purchase #5	$37.92	11.459%	$42.2653	$42.27	$42.25	$42.30
Purchase #6	$48.60	9.702%	$53.3152	$53.32	$53.30	$53.30
Purchase #7	$157.76	11.222%	$175.4638	$175.46	$175.45	$175.50
7 purchase totals =	$698.98		$761.8925	$761.90	$761.80	$761.90