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	$154.86	11.557%	$172.7572	$172.76	$172.75	$172.80
Purchase #2	$246.99	4.674%	$258.5343	$258.53	$258.55	$258.50
Purchase #3	$120.56	6.636%	$128.5604	$128.56	$128.55	$128.60
Purchase #4	$136.37	6.757%	$145.5845	$145.58	$145.60	$145.60
Purchase #5	$100.25	3.657%	$103.9161	$103.92	$103.90	$103.90
Purchase #6	$81.72	10.223%	$90.0742	$90.07	$90.05	$90.10
Purchase #7	$208.35	7.712%	$224.418	$224.42	$224.40	$224.40
7 purchase totals =	$1,049.10		$1,123.8447	$1,123.84	$1,123.80	$1,123.90