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	$146.37	11.105%	$162.6244	$162.62	$162.60	$162.60
Purchase #2	$182.73	12.528%	$205.6224	$205.62	$205.60	$205.60
Purchase #3	$169.62	13.685%	$192.8325	$192.83	$192.85	$192.80
Purchase #4	$138.69	4.523%	$144.9629	$144.96	$144.95	$145.00
Purchase #5	$180.42	13.674%	$205.0906	$205.09	$205.10	$205.10
Purchase #6	$235.51	8.455%	$255.4224	$255.42	$255.40	$255.40
Purchase #7	$133.65	5.841%	$141.4565	$141.46	$141.45	$141.50
7 purchase totals =	$1,186.99		$1,308.0117	$1,308.00	$1,307.95	$1,308.00