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	$144.77	8.182%	$156.6151	$156.62	$156.60	$156.60
Purchase #2	$47.74	7.549%	$51.3439	$51.34	$51.35	$51.30
Purchase #3	$81.66	9.556%	$89.4634	$89.46	$89.45	$89.50
Purchase #4	$219.52	8.801%	$238.84	$238.84	$238.85	$238.80
Purchase #5	$112.78	5.491%	$118.9727	$118.97	$118.95	$119.00
Purchase #6	$121.29	13.231%	$137.3379	$137.34	$137.35	$137.30
Purchase #7	$139.65	9.569%	$153.0131	$153.01	$153.00	$153.00
7 purchase totals =	$867.41		$945.5861	$945.58	$945.55	$945.50