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	$47.84	10.675%	$52.9469	$52.95	$52.95	$52.90
Purchase #2	$58.98	11.537%	$65.7845	$65.78	$65.80	$65.80
Purchase #3	$95.52	4.265%	$99.5939	$99.59	$99.60	$99.60
Purchase #4	$173.90	7.307%	$186.6069	$186.61	$186.60	$186.60
Purchase #5	$249.86	10.306%	$275.6106	$275.61	$275.60	$275.60
Purchase #6	$120.81	9.573%	$132.3751	$132.38	$132.40	$132.40
Purchase #7	$19.26	12.495%	$21.6665	$21.67	$21.65	$21.70
7 purchase totals =	$766.17		$834.5844	$834.59	$834.60	$834.60