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	$200.84	8.116%	$217.1402	$217.14	$217.15	$217.10
Purchase #2	$177.68	7.413%	$190.8514	$190.85	$190.85	$190.90
Purchase #3	$235.51	11.437%	$262.4453	$262.45	$262.45	$262.40
Purchase #4	$136.25	3.825%	$141.4616	$141.46	$141.45	$141.50
Purchase #5	$173.87	3.113%	$179.2826	$179.28	$179.30	$179.30
Purchase #6	$41.35	10.295%	$45.607	$45.61	$45.60	$45.60
Purchase #7	$97.62	7.347%	$104.7921	$104.79	$104.80	$104.80
7 purchase totals =	$1,063.12		$1,141.5802	$1,141.58	$1,141.60	$1,141.60