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	$34.31	10.292%	$37.8412	$37.84	$37.85	$37.80
Purchase #2	$32.39	7.182%	$34.7162	$34.72	$34.70	$34.70
Purchase #3	$21.51	4.350%	$22.4457	$22.45	$22.45	$22.40
Purchase #4	$124.98	5.637%	$132.0251	$132.03	$132.05	$132.00
Purchase #5	$217.52	9.817%	$238.8739	$238.87	$238.85	$238.90
Purchase #6	$95.50	4.739%	$100.0257	$100.03	$100.05	$100.00
Purchase #7	$183.27	5.241%	$192.8752	$192.88	$192.90	$192.90
7 purchase totals =	$709.48		$758.8030	$758.82	$758.85	$758.70