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	$104.77	10.826%	$116.1124	$116.11	$116.10	$116.10
Purchase #2	$200.36	4.572%	$209.5205	$209.52	$209.50	$209.50
Purchase #3	$112.64	11.726%	$125.8482	$125.85	$125.85	$125.80
Purchase #4	$133.73	5.752%	$141.4221	$141.42	$141.40	$141.40
Purchase #5	$26.34	3.651%	$27.3017	$27.30	$27.30	$27.30
Purchase #6	$204.61	6.485%	$217.879	$217.88	$217.90	$217.90
Purchase #7	$121.37	8.277%	$131.4158	$131.42	$131.40	$131.40
7 purchase totals =	$903.82		$969.4997	$969.50	$969.45	$969.40