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	$164.27	4.763%	$172.0942	$172.09	$172.10	$172.10
Purchase #2	$168.95	9.641%	$185.2385	$185.24	$185.25	$185.20
Purchase #3	$43.47	10.744%	$48.1404	$48.14	$48.15	$48.10
Purchase #4	$52.97	4.532%	$55.3706	$55.37	$55.35	$55.40
Purchase #5	$38.34	6.303%	$40.7566	$40.76	$40.75	$40.80
Purchase #6	$192.50	8.449%	$208.7643	$208.76	$208.75	$208.80
Purchase #7	$67.27	12.789%	$75.8732	$75.87	$75.85	$75.90
7 purchase totals =	$727.77		$786.2378	$786.23	$786.20	$786.30