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	$235.69	9.854%	$258.9149	$258.91	$258.90	$258.90
Purchase #2	$10.62	9.868%	$11.668	$11.67	$11.65	$11.70
Purchase #3	$172.27	7.730%	$185.5865	$185.59	$185.60	$185.60
Purchase #4	$60.66	10.271%	$66.8904	$66.89	$66.90	$66.90
Purchase #5	$242.61	8.798%	$263.9548	$263.95	$263.95	$264.00
Purchase #6	$25.48	8.282%	$27.5903	$27.59	$27.60	$27.60
Purchase #7	$68.99	5.603%	$72.8555	$72.86	$72.85	$72.90
7 purchase totals =	$816.32		$887.4604	$887.46	$887.45	$887.60