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	$86.67	4.705%	$90.7478	$90.75	$90.75	$90.70
Purchase #2	$69.92	8.747%	$76.0359	$76.04	$76.05	$76.00
Purchase #3	$140.90	7.766%	$151.8423	$151.84	$151.85	$151.80
Purchase #4	$61.96	7.831%	$66.8121	$66.81	$66.80	$66.80
Purchase #5	$71.42	6.793%	$76.2716	$76.27	$76.25	$76.30
Purchase #6	$215.30	3.838%	$223.5632	$223.56	$223.55	$223.60
Purchase #7	$28.95	13.317%	$32.8053	$32.81	$32.80	$32.80
7 purchase totals =	$675.12		$718.0782	$718.08	$718.05	$718.00