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	$32.32	10.198%	$35.616	$35.62	$35.60	$35.60
Purchase #2	$48.85	5.809%	$51.6877	$51.69	$51.70	$51.70
Purchase #3	$27.29	11.709%	$30.4854	$30.49	$30.50	$30.50
Purchase #4	$63.55	12.527%	$71.5109	$71.51	$71.50	$71.50
Purchase #5	$82.80	9.748%	$90.8713	$90.87	$90.85	$90.90
Purchase #6	$43.43	13.241%	$49.1806	$49.18	$49.20	$49.20
Purchase #7	$203.45	10.433%	$224.6759	$224.68	$224.70	$224.70
7 purchase totals =	$501.69		$554.0278	$554.04	$554.05	$554.10