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	$137.32	11.617%	$153.2725	$153.27	$153.25	$153.30
Purchase #2	$241.48	5.746%	$255.3554	$255.36	$255.35	$255.40
Purchase #3	$231.69	4.268%	$241.5785	$241.58	$241.60	$241.60
Purchase #4	$170.43	10.145%	$187.7201	$187.72	$187.70	$187.70
Purchase #5	$79.69	10.110%	$87.7467	$87.75	$87.75	$87.70
Purchase #6	$215.28	5.729%	$227.6134	$227.61	$227.60	$227.60
Purchase #7	$139.67	6.296%	$148.4636	$148.46	$148.45	$148.50
7 purchase totals =	$1,215.56		$1,301.7502	$1,301.75	$1,301.70	$1,301.80