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	$64.68	10.311%	$71.3492	$71.35	$71.35	$71.30
Purchase #2	$202.75	12.400%	$227.891	$227.89	$227.90	$227.90
Purchase #3	$98.54	7.473%	$105.9039	$105.90	$105.90	$105.90
Purchase #4	$129.68	7.635%	$139.5811	$139.58	$139.60	$139.60
Purchase #5	$187.37	8.620%	$203.5213	$203.52	$203.50	$203.50
Purchase #6	$52.52	3.114%	$54.1555	$54.16	$54.15	$54.20
Purchase #7	$52.37	13.841%	$59.6185	$59.62	$59.60	$59.60
7 purchase totals =	$787.91		$862.0205	$862.02	$862.00	$862.00