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	$57.32	4.450%	$59.8707	$59.87	$59.85	$59.90
Purchase #2	$60.80	11.235%	$67.6309	$67.63	$67.65	$67.60
Purchase #3	$149.99	12.610%	$168.9037	$168.90	$168.90	$168.90
Purchase #4	$37.90	12.167%	$42.5113	$42.51	$42.50	$42.50
Purchase #5	$60.73	8.294%	$65.7669	$65.77	$65.75	$65.80
Purchase #6	$27.40	9.596%	$30.0293	$30.03	$30.05	$30.00
Purchase #7	$116.50	8.349%	$126.2266	$126.23	$126.25	$126.20
7 purchase totals =	$510.64		$560.9394	$560.94	$560.95	$560.90