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	$161.66	9.377%	$176.8189	$176.82	$176.80	$176.80
Purchase #2	$144.56	4.711%	$151.3702	$151.37	$151.35	$151.40
Purchase #3	$227.78	4.385%	$237.7682	$237.77	$237.75	$237.80
Purchase #4	$172.52	10.291%	$190.274	$190.27	$190.25	$190.30
Purchase #5	$163.86	9.287%	$179.0777	$179.08	$179.10	$179.10
Purchase #6	$173.69	6.799%	$185.4992	$185.50	$185.50	$185.50
Purchase #7	$38.85	10.289%	$42.8473	$42.85	$42.85	$42.80
7 purchase totals =	$1,082.92		$1,163.6555	$1,163.66	$1,163.60	$1,163.70