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	$206.70	7.683%	$222.5808	$222.58	$222.60	$222.60
Purchase #2	$98.34	10.116%	$108.2881	$108.29	$108.30	$108.30
Purchase #3	$85.28	10.431%	$94.1756	$94.18	$94.20	$94.20
Purchase #4	$140.78	6.166%	$149.4605	$149.46	$149.45	$149.50
Purchase #5	$165.37	6.509%	$176.1339	$176.13	$176.15	$176.10
Purchase #6	$39.25	8.317%	$42.5144	$42.51	$42.50	$42.50
Purchase #7	$83.55	13.260%	$94.6287	$94.63	$94.65	$94.60
7 purchase totals =	$819.27		$887.7820	$887.78	$887.85	$887.80