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	$208.90	5.723%	$220.8553	$220.86	$220.85	$220.90
Purchase #2	$33.76	4.824%	$35.3886	$35.39	$35.40	$35.40
Purchase #3	$99.94	9.452%	$109.3863	$109.39	$109.40	$109.40
Purchase #4	$235.78	4.661%	$246.7697	$246.77	$246.75	$246.80
Purchase #5	$207.97	4.716%	$217.7779	$217.78	$217.80	$217.80
Purchase #6	$205.38	5.695%	$217.0764	$217.08	$217.10	$217.10
Purchase #7	$144.88	5.570%	$152.9498	$152.95	$152.95	$152.90
7 purchase totals =	$1,136.61		$1,200.2040	$1,200.22	$1,200.25	$1,200.30