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	$182.60	9.182%	$199.3663	$199.37	$199.35	$199.40
Purchase #2	$229.47	11.189%	$255.1454	$255.15	$255.15	$255.10
Purchase #3	$50.41	4.666%	$52.7621	$52.76	$52.75	$52.80
Purchase #4	$101.53	11.166%	$112.8668	$112.87	$112.85	$112.90
Purchase #5	$179.27	3.452%	$185.4584	$185.46	$185.45	$185.50
Purchase #6	$188.82	8.693%	$205.2341	$205.23	$205.25	$205.20
Purchase #7	$186.62	13.496%	$211.8062	$211.81	$211.80	$211.80
7 purchase totals =	$1,118.72		$1,222.6393	$1,222.65	$1,222.60	$1,222.70