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	$48.37	9.211%	$52.8254	$52.83	$52.85	$52.80
Purchase #2	$49.91	7.449%	$53.6278	$53.63	$53.65	$53.60
Purchase #3	$213.52	4.311%	$222.7248	$222.72	$222.70	$222.70
Purchase #4	$86.81	10.191%	$95.6568	$95.66	$95.65	$95.70
Purchase #5	$216.52	9.682%	$237.4835	$237.48	$237.50	$237.50
Purchase #6	$198.97	9.259%	$217.3926	$217.39	$217.40	$217.40
Purchase #7	$72.87	7.616%	$78.4198	$78.42	$78.40	$78.40
7 purchase totals =	$886.97		$958.1307	$958.13	$958.15	$958.10