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	$128.34	3.308%	$132.5855	$132.59	$132.60	$132.60
Purchase #2	$11.82	6.808%	$12.6247	$12.62	$12.60	$12.60
Purchase #3	$123.64	3.346%	$127.777	$127.78	$127.80	$127.80
Purchase #4	$107.88	4.668%	$112.9158	$112.92	$112.90	$112.90
Purchase #5	$57.29	7.409%	$61.5346	$61.53	$61.55	$61.50
Purchase #6	$141.66	7.278%	$151.97	$151.97	$151.95	$152.00
Purchase #7	$145.96	7.836%	$157.3974	$157.40	$157.40	$157.40
7 purchase totals =	$716.59		$756.8050	$756.81	$756.80	$756.80