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	$179.71	9.742%	$197.2173	$197.22	$197.20	$197.20
Purchase #2	$173.89	9.361%	$190.1678	$190.17	$190.15	$190.20
Purchase #3	$195.92	10.554%	$216.5974	$216.60	$216.60	$216.60
Purchase #4	$33.51	11.466%	$37.3523	$37.35	$37.35	$37.40
Purchase #5	$82.39	9.645%	$90.3365	$90.34	$90.35	$90.30
Purchase #6	$223.42	13.866%	$254.3994	$254.40	$254.40	$254.40
Purchase #7	$151.96	5.295%	$160.0063	$160.01	$160.00	$160.00
7 purchase totals =	$1,040.80		$1,146.0770	$1,146.09	$1,146.05	$1,146.10