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	$17.35	10.504%	$19.1724	$19.17	$19.15	$19.20
Purchase #2	$140.99	11.421%	$157.0925	$157.09	$157.10	$157.10
Purchase #3	$54.55	8.702%	$59.2969	$59.30	$59.30	$59.30
Purchase #4	$56.81	5.177%	$59.7511	$59.75	$59.75	$59.80
Purchase #5	$185.82	12.413%	$208.8858	$208.89	$208.90	$208.90
Purchase #6	$168.73	10.669%	$186.7318	$186.73	$186.75	$186.70
Purchase #7	$31.66	12.240%	$35.5352	$35.54	$35.55	$35.50
7 purchase totals =	$655.91		$726.4657	$726.47	$726.50	$726.50