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	$96.35	7.529%	$103.6042	$103.60	$103.60	$103.60
Purchase #2	$28.78	10.598%	$31.8301	$31.83	$31.85	$31.80
Purchase #3	$242.49	11.528%	$270.4442	$270.44	$270.45	$270.40
Purchase #4	$207.84	10.798%	$230.2826	$230.28	$230.30	$230.30
Purchase #5	$230.84	5.724%	$244.0533	$244.05	$244.05	$244.10
Purchase #6	$85.34	5.546%	$90.073	$90.07	$90.05	$90.10
Purchase #7	$204.81	10.387%	$226.0836	$226.08	$226.10	$226.10
7 purchase totals =	$1,096.45		$1,196.3710	$1,196.35	$1,196.40	$1,196.40