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	$100.98	8.853%	$109.9198	$109.92	$109.90	$109.90
Purchase #2	$106.31	9.600%	$116.5158	$116.52	$116.50	$116.50
Purchase #3	$85.45	5.457%	$90.113	$90.11	$90.10	$90.10
Purchase #4	$133.64	9.814%	$146.7554	$146.76	$146.75	$146.80
Purchase #5	$100.96	10.287%	$111.3458	$111.35	$111.35	$111.30
Purchase #6	$112.33	8.324%	$121.6803	$121.68	$121.70	$121.70
Purchase #7	$61.47	8.778%	$66.8658	$66.87	$66.85	$66.90
7 purchase totals =	$701.14		$763.1959	$763.21	$763.15	$763.20