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	$95.54	11.590%	$106.6131	$106.61	$106.60	$106.60
Purchase #2	$90.32	5.468%	$95.2587	$95.26	$95.25	$95.30
Purchase #3	$103.54	12.522%	$116.5053	$116.51	$116.50	$116.50
Purchase #4	$87.47	3.601%	$90.6198	$90.62	$90.60	$90.60
Purchase #5	$245.27	11.181%	$272.6936	$272.69	$272.70	$272.70
Purchase #6	$125.81	10.564%	$139.1006	$139.10	$139.10	$139.10
Purchase #7	$148.97	8.453%	$161.5624	$161.56	$161.55	$161.60
7 purchase totals =	$896.92		$982.3535	$982.35	$982.30	$982.40