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	$56.40	10.361%	$62.2436	$62.24	$62.25	$62.20
Purchase #2	$168.37	12.852%	$190.0089	$190.01	$190.00	$190.00
Purchase #3	$204.46	8.820%	$222.4934	$222.49	$222.50	$222.50
Purchase #4	$81.89	3.400%	$84.6743	$84.67	$84.65	$84.70
Purchase #5	$39.67	12.175%	$44.4998	$44.50	$44.50	$44.50
Purchase #6	$90.83	10.624%	$100.4798	$100.48	$100.50	$100.50
Purchase #7	$70.30	8.463%	$76.2495	$76.25	$76.25	$76.20
7 purchase totals =	$711.92		$780.6493	$780.64	$780.65	$780.60