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	$30.34	8.267%	$32.8482	$32.85	$32.85	$32.80
Purchase #2	$64.94	11.638%	$72.4977	$72.50	$72.50	$72.50
Purchase #3	$205.97	5.637%	$217.5805	$217.58	$217.60	$217.60
Purchase #4	$125.62	12.723%	$141.6026	$141.60	$141.60	$141.60
Purchase #5	$112.35	12.148%	$125.9983	$126.00	$126.00	$126.00
Purchase #6	$32.86	6.202%	$34.898	$34.90	$34.90	$34.90
Purchase #7	$56.26	5.751%	$59.4955	$59.50	$59.50	$59.50
7 purchase totals =	$628.34		$684.9208	$684.93	$684.95	$684.90