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	$89.25	10.492%	$98.6141	$98.61	$98.60	$98.60
Purchase #2	$56.66	11.874%	$63.3878	$63.39	$63.40	$63.40
Purchase #3	$41.93	3.182%	$43.2642	$43.26	$43.25	$43.30
Purchase #4	$67.66	13.146%	$76.5546	$76.55	$76.55	$76.60
Purchase #5	$172.61	11.503%	$192.4653	$192.47	$192.45	$192.50
Purchase #6	$141.89	12.688%	$159.893	$159.89	$159.90	$159.90
Purchase #7	$236.70	5.450%	$249.6002	$249.60	$249.60	$249.60
7 purchase totals =	$806.70		$883.7792	$883.77	$883.75	$883.90