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	$58.82	6.321%	$62.538	$62.54	$62.55	$62.50
Purchase #2	$86.54	10.277%	$95.4337	$95.43	$95.45	$95.40
Purchase #3	$11.26	10.389%	$12.4298	$12.43	$12.45	$12.40
Purchase #4	$146.55	5.443%	$154.5267	$154.53	$154.55	$154.50
Purchase #5	$52.80	6.855%	$56.4194	$56.42	$56.40	$56.40
Purchase #6	$222.48	5.370%	$234.4272	$234.43	$234.45	$234.40
Purchase #7	$21.45	6.860%	$22.9215	$22.92	$22.90	$22.90
7 purchase totals =	$599.90		$638.6963	$638.70	$638.75	$638.50