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	$55.85	12.169%	$62.6464	$62.65	$62.65	$62.60
Purchase #2	$90.96	12.364%	$102.2063	$102.21	$102.20	$102.20
Purchase #3	$12.27	12.199%	$13.7668	$13.77	$13.75	$13.80
Purchase #4	$228.75	11.725%	$255.5709	$255.57	$255.55	$255.60
Purchase #5	$78.56	13.296%	$89.0053	$89.01	$89.00	$89.00
Purchase #6	$111.51	13.186%	$126.2137	$126.21	$126.20	$126.20
Purchase #7	$52.51	10.753%	$58.1564	$58.16	$58.15	$58.20
7 purchase totals =	$630.41		$707.5658	$707.58	$707.50	$707.60