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	$62.87	5.565%	$66.3687	$66.37	$66.35	$66.40
Purchase #2	$213.88	11.560%	$238.6045	$238.60	$238.60	$238.60
Purchase #3	$228.81	4.661%	$239.4748	$239.47	$239.45	$239.50
Purchase #4	$85.26	11.363%	$94.9481	$94.95	$94.95	$94.90
Purchase #5	$153.63	7.260%	$164.7835	$164.78	$164.80	$164.80
Purchase #6	$66.67	10.365%	$73.5803	$73.58	$73.60	$73.60
Purchase #7	$169.27	5.495%	$178.5714	$178.57	$178.55	$178.60
7 purchase totals =	$980.39		$1,056.3313	$1,056.32	$1,056.30	$1,056.40