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	$87.82	3.262%	$90.6847	$90.68	$90.70	$90.70
Purchase #2	$164.66	4.550%	$172.152	$172.15	$172.15	$172.20
Purchase #3	$226.89	12.656%	$255.6052	$255.61	$255.60	$255.60
Purchase #4	$190.73	7.403%	$204.8497	$204.85	$204.85	$204.80
Purchase #5	$95.93	13.725%	$109.0964	$109.10	$109.10	$109.10
Purchase #6	$242.54	10.139%	$267.1311	$267.13	$267.15	$267.10
Purchase #7	$152.67	3.746%	$158.389	$158.39	$158.40	$158.40
7 purchase totals =	$1,161.24		$1,257.9081	$1,257.91	$1,257.95	$1,257.90