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	$140.86	3.256%	$145.4464	$145.45	$145.45	$145.40
Purchase #2	$219.81	12.561%	$247.4203	$247.42	$247.40	$247.40
Purchase #3	$54.96	8.316%	$59.5305	$59.53	$59.55	$59.50
Purchase #4	$48.45	3.629%	$50.2083	$50.21	$50.20	$50.20
Purchase #5	$213.51	8.219%	$231.0584	$231.06	$231.05	$231.10
Purchase #6	$93.53	6.347%	$99.4663	$99.47	$99.45	$99.50
Purchase #7	$125.71	5.824%	$133.0314	$133.03	$133.05	$133.00
7 purchase totals =	$896.83		$966.1616	$966.17	$966.15	$966.10