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	$98.51	12.683%	$111.004	$111.00	$111.00	$111.00
Purchase #2	$13.81	12.722%	$15.5669	$15.57	$15.55	$15.60
Purchase #3	$234.68	6.476%	$249.8779	$249.88	$249.90	$249.90
Purchase #4	$8.81	5.748%	$9.3164	$9.32	$9.30	$9.30
Purchase #5	$10.59	10.426%	$11.6941	$11.69	$11.70	$11.70
Purchase #6	$86.78	11.135%	$96.443	$96.44	$96.45	$96.40
Purchase #7	$112.97	9.406%	$123.596	$123.60	$123.60	$123.60
7 purchase totals =	$566.15		$617.4983	$617.50	$617.50	$617.50