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	$88.28	7.186%	$94.6238	$94.62	$94.60	$94.60
Purchase #2	$113.75	8.852%	$123.8192	$123.82	$123.80	$123.80
Purchase #3	$38.99	8.373%	$42.2546	$42.25	$42.25	$42.30
Purchase #4	$9.51	11.570%	$10.6103	$10.61	$10.60	$10.60
Purchase #5	$46.98	13.769%	$53.4487	$53.45	$53.45	$53.40
Purchase #6	$228.42	5.739%	$241.529	$241.53	$241.55	$241.50
Purchase #7	$237.63	13.627%	$270.0118	$270.01	$270.00	$270.00
7 purchase totals =	$763.56		$836.2974	$836.29	$836.25	$836.20