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	$83.44	9.580%	$91.4336	$91.43	$91.45	$91.40
Purchase #2	$17.52	5.438%	$18.4727	$18.47	$18.45	$18.50
Purchase #3	$75.47	9.108%	$82.3438	$82.34	$82.35	$82.30
Purchase #4	$100.29	10.870%	$111.1915	$111.19	$111.20	$111.20
Purchase #5	$244.57	8.863%	$266.2462	$266.25	$266.25	$266.20
Purchase #6	$71.94	13.265%	$81.4828	$81.48	$81.50	$81.50
Purchase #7	$9.98	5.717%	$10.5506	$10.55	$10.55	$10.60
7 purchase totals =	$603.21		$661.7212	$661.71	$661.75	$661.70