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	$175.89	11.482%	$196.0857	$196.09	$196.10	$196.10
Purchase #2	$50.64	3.330%	$52.3263	$52.33	$52.35	$52.30
Purchase #3	$144.80	5.229%	$152.3716	$152.37	$152.35	$152.40
Purchase #4	$97.85	13.617%	$111.1742	$111.17	$111.15	$111.20
Purchase #5	$25.25	8.383%	$27.3667	$27.37	$27.35	$27.40
Purchase #6	$249.67	5.264%	$262.8126	$262.81	$262.80	$262.80
Purchase #7	$184.65	3.164%	$190.4923	$190.49	$190.50	$190.50
7 purchase totals =	$928.75		$992.6294	$992.63	$992.60	$992.70