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	$56.78	4.609%	$59.397	$59.40	$59.40	$59.40
Purchase #2	$97.88	6.422%	$104.1659	$104.17	$104.15	$104.20
Purchase #3	$26.55	10.551%	$29.3513	$29.35	$29.35	$29.40
Purchase #4	$126.36	3.368%	$130.6158	$130.62	$130.60	$130.60
Purchase #5	$29.27	8.559%	$31.7752	$31.78	$31.80	$31.80
Purchase #6	$230.54	11.182%	$256.319	$256.32	$256.30	$256.30
Purchase #7	$217.51	11.333%	$242.1604	$242.16	$242.15	$242.20
7 purchase totals =	$784.89		$853.7846	$853.80	$853.75	$853.90