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	$116.72	9.204%	$127.4629	$127.46	$127.45	$127.50
Purchase #2	$33.81	9.687%	$37.0852	$37.09	$37.10	$37.10
Purchase #3	$216.83	9.317%	$237.0321	$237.03	$237.05	$237.00
Purchase #4	$214.96	11.151%	$238.9302	$238.93	$238.95	$238.90
Purchase #5	$115.86	9.831%	$127.2502	$127.25	$127.25	$127.30
Purchase #6	$16.90	9.472%	$18.5008	$18.50	$18.50	$18.50
Purchase #7	$123.72	7.324%	$132.7813	$132.78	$132.80	$132.80
7 purchase totals =	$838.80		$919.0427	$919.04	$919.10	$919.10