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	$210.38	11.122%	$233.7785	$233.78	$233.80	$233.80
Purchase #2	$213.58	9.129%	$233.0777	$233.08	$233.10	$233.10
Purchase #3	$92.66	12.679%	$104.4084	$104.41	$104.40	$104.40
Purchase #4	$185.28	13.308%	$209.9371	$209.94	$209.95	$209.90
Purchase #5	$104.45	12.404%	$117.406	$117.41	$117.40	$117.40
Purchase #6	$77.87	3.178%	$80.3447	$80.34	$80.35	$80.30
Purchase #7	$94.48	11.554%	$105.3962	$105.40	$105.40	$105.40
7 purchase totals =	$978.70		$1,084.3486	$1,084.36	$1,084.40	$1,084.30