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	$86.47	6.455%	$92.0516	$92.05	$92.05	$92.10
Purchase #2	$159.60	5.479%	$168.3445	$168.34	$168.35	$168.30
Purchase #3	$47.77	7.429%	$51.3188	$51.32	$51.30	$51.30
Purchase #4	$165.50	4.495%	$172.9392	$172.94	$172.95	$172.90
Purchase #5	$12.99	11.515%	$14.4858	$14.49	$14.50	$14.50
Purchase #6	$162.53	5.144%	$170.8905	$170.89	$170.90	$170.90
Purchase #7	$134.90	10.853%	$149.5407	$149.54	$149.55	$149.50
7 purchase totals =	$769.76		$819.5711	$819.57	$819.60	$819.50