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	$87.53	4.330%	$91.32	$91.32	$91.30	$91.30
Purchase #2	$38.64	9.423%	$42.281	$42.28	$42.30	$42.30
Purchase #3	$133.59	4.245%	$139.2609	$139.26	$139.25	$139.30
Purchase #4	$117.95	3.336%	$121.8848	$121.88	$121.90	$121.90
Purchase #5	$38.67	7.230%	$41.4658	$41.47	$41.45	$41.50
Purchase #6	$224.53	7.768%	$241.9715	$241.97	$241.95	$242.00
Purchase #7	$55.90	8.240%	$60.5062	$60.51	$60.50	$60.50
7 purchase totals =	$696.81		$738.6902	$738.69	$738.65	$738.80