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	$54.94	6.456%	$58.4869	$58.49	$58.50	$58.50
Purchase #2	$166.36	5.167%	$174.9558	$174.96	$174.95	$175.00
Purchase #3	$30.29	10.811%	$33.5647	$33.56	$33.55	$33.60
Purchase #4	$226.72	13.716%	$257.8169	$257.82	$257.80	$257.80
Purchase #5	$215.86	3.565%	$223.5554	$223.56	$223.55	$223.60
Purchase #6	$213.43	5.172%	$224.4686	$224.47	$224.45	$224.50
Purchase #7	$101.28	6.758%	$108.1245	$108.12	$108.10	$108.10
7 purchase totals =	$1,008.88		$1,080.9728	$1,080.98	$1,080.90	$1,081.10