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	$108.96	4.835%	$114.2282	$114.23	$114.25	$114.20
Purchase #2	$34.68	8.485%	$37.6226	$37.62	$37.60	$37.60
Purchase #3	$37.37	8.509%	$40.5498	$40.55	$40.55	$40.50
Purchase #4	$37.90	9.644%	$41.5551	$41.56	$41.55	$41.60
Purchase #5	$13.53	4.745%	$14.172	$14.17	$14.15	$14.20
Purchase #6	$232.37	12.698%	$261.8763	$261.88	$261.90	$261.90
Purchase #7	$6.65	9.129%	$7.2571	$7.26	$7.25	$7.30
7 purchase totals =	$471.46		$517.2611	$517.27	$517.25	$517.30