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	$93.76	12.773%	$105.736	$105.74	$105.75	$105.70
Purchase #2	$27.78	11.811%	$31.0611	$31.06	$31.05	$31.10
Purchase #3	$172.85	9.835%	$189.8498	$189.85	$189.85	$189.80
Purchase #4	$127.99	10.762%	$141.7643	$141.76	$141.75	$141.80
Purchase #5	$97.79	8.210%	$105.8186	$105.82	$105.80	$105.80
Purchase #6	$77.92	7.431%	$83.7102	$83.71	$83.70	$83.70
Purchase #7	$25.94	6.270%	$27.5664	$27.57	$27.55	$27.60
7 purchase totals =	$624.03		$685.5064	$685.51	$685.45	$685.50