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	$32.57	9.102%	$35.5345	$35.53	$35.55	$35.50
Purchase #2	$147.72	13.536%	$167.7154	$167.72	$167.70	$167.70
Purchase #3	$92.61	5.715%	$97.9027	$97.90	$97.90	$97.90
Purchase #4	$51.34	9.159%	$56.0422	$56.04	$56.05	$56.00
Purchase #5	$132.75	9.392%	$145.2179	$145.22	$145.20	$145.20
Purchase #6	$126.57	3.609%	$131.1379	$131.14	$131.15	$131.10
Purchase #7	$164.27	5.205%	$172.8203	$172.82	$172.80	$172.80
7 purchase totals =	$747.83		$806.3709	$806.37	$806.35	$806.20