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	$116.40	13.651%	$132.2898	$132.29	$132.30	$132.30
Purchase #2	$104.87	12.447%	$117.9232	$117.92	$117.90	$117.90
Purchase #3	$82.72	6.841%	$88.3789	$88.38	$88.40	$88.40
Purchase #4	$207.86	6.740%	$221.8698	$221.87	$221.85	$221.90
Purchase #5	$86.39	5.483%	$91.1268	$91.13	$91.15	$91.10
Purchase #6	$124.57	10.755%	$137.9675	$137.97	$137.95	$138.00
Purchase #7	$89.69	3.567%	$92.8892	$92.89	$92.90	$92.90
7 purchase totals =	$812.50		$882.4452	$882.45	$882.45	$882.50