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	$151.92	9.789%	$166.7914	$166.79	$166.80	$166.80
Purchase #2	$247.48	3.148%	$255.2707	$255.27	$255.25	$255.30
Purchase #3	$81.48	9.473%	$89.1986	$89.20	$89.20	$89.20
Purchase #4	$92.92	11.648%	$103.7433	$103.74	$103.75	$103.70
Purchase #5	$10.76	4.622%	$11.2573	$11.26	$11.25	$11.30
Purchase #6	$11.82	12.473%	$13.2943	$13.29	$13.30	$13.30
Purchase #7	$77.96	7.538%	$83.8366	$83.84	$83.85	$83.80
7 purchase totals =	$674.34		$723.3922	$723.39	$723.40	$723.40