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	$62.71	4.603%	$65.5965	$65.60	$65.60	$65.60
Purchase #2	$11.30	9.514%	$12.3751	$12.38	$12.40	$12.40
Purchase #3	$199.40	5.150%	$209.6691	$209.67	$209.65	$209.70
Purchase #4	$66.71	8.812%	$72.5885	$72.59	$72.60	$72.60
Purchase #5	$152.68	9.636%	$167.3922	$167.39	$167.40	$167.40
Purchase #6	$131.69	4.256%	$137.2947	$137.29	$137.30	$137.30
Purchase #7	$84.32	13.650%	$95.8297	$95.83	$95.85	$95.80
7 purchase totals =	$708.81		$760.7458	$760.75	$760.80	$760.80