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	$244.47	5.518%	$257.9599	$257.96	$257.95	$258.00
Purchase #2	$71.68	9.482%	$78.4767	$78.48	$78.50	$78.50
Purchase #3	$213.80	3.669%	$221.6443	$221.64	$221.65	$221.60
Purchase #4	$152.58	4.264%	$159.086	$159.09	$159.10	$159.10
Purchase #5	$107.95	5.348%	$113.7232	$113.72	$113.70	$113.70
Purchase #6	$123.69	7.441%	$132.8938	$132.89	$132.90	$132.90
Purchase #7	$222.40	4.636%	$232.7105	$232.71	$232.70	$232.70
7 purchase totals =	$1,136.57		$1,196.4944	$1,196.49	$1,196.50	$1,196.50