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	$31.25	12.409%	$35.1278	$35.13	$35.15	$35.10
Purchase #2	$181.83	10.441%	$200.8149	$200.81	$200.80	$200.80
Purchase #3	$34.89	13.638%	$39.6483	$39.65	$39.65	$39.60
Purchase #4	$240.78	13.176%	$272.5052	$272.51	$272.50	$272.50
Purchase #5	$153.83	13.693%	$174.8939	$174.89	$174.90	$174.90
Purchase #6	$221.58	12.150%	$248.502	$248.50	$248.50	$248.50
Purchase #7	$91.66	11.456%	$102.1606	$102.16	$102.15	$102.20
7 purchase totals =	$955.82		$1,073.6527	$1,073.65	$1,073.65	$1,073.60