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	$122.65	7.772%	$132.1824	$132.18	$132.20	$132.20
Purchase #2	$83.28	13.466%	$94.4945	$94.49	$94.50	$94.50
Purchase #3	$179.70	13.572%	$204.0889	$204.09	$204.10	$204.10
Purchase #4	$85.30	5.837%	$90.279	$90.28	$90.30	$90.30
Purchase #5	$53.76	12.509%	$60.4848	$60.48	$60.50	$60.50
Purchase #6	$32.94	13.484%	$37.3816	$37.38	$37.40	$37.40
Purchase #7	$149.59	5.509%	$157.8309	$157.83	$157.85	$157.80
7 purchase totals =	$707.22		$776.7421	$776.73	$776.85	$776.80