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	$87.72	8.392%	$95.0815	$95.08	$95.10	$95.10
Purchase #2	$46.40	6.792%	$49.5515	$49.55	$49.55	$49.60
Purchase #3	$46.60	10.648%	$51.562	$51.56	$51.55	$51.60
Purchase #4	$178.74	9.766%	$196.1957	$196.20	$196.20	$196.20
Purchase #5	$29.64	9.644%	$32.4985	$32.50	$32.50	$32.50
Purchase #6	$135.93	10.866%	$150.7002	$150.70	$150.70	$150.70
Purchase #7	$91.90	11.615%	$102.5742	$102.57	$102.55	$102.60
7 purchase totals =	$616.93		$678.1636	$678.16	$678.15	$678.30