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	$212.94	6.284%	$226.3211	$226.32	$226.30	$226.30
Purchase #2	$87.58	13.655%	$99.539	$99.54	$99.55	$99.50
Purchase #3	$183.52	3.794%	$190.4827	$190.48	$190.50	$190.50
Purchase #4	$117.90	12.172%	$132.2508	$132.25	$132.25	$132.30
Purchase #5	$203.96	8.794%	$221.8962	$221.90	$221.90	$221.90
Purchase #6	$55.68	8.659%	$60.5013	$60.50	$60.50	$60.50
Purchase #7	$190.80	13.866%	$217.2563	$217.26	$217.25	$217.30
7 purchase totals =	$1,052.38		$1,148.2474	$1,148.25	$1,148.25	$1,148.30