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	$202.94	9.517%	$222.2538	$222.25	$222.25	$222.30
Purchase #2	$94.31	12.381%	$105.9865	$105.99	$106.00	$106.00
Purchase #3	$132.85	7.735%	$143.1259	$143.13	$143.15	$143.10
Purchase #4	$39.67	5.346%	$41.7908	$41.79	$41.80	$41.80
Purchase #5	$37.53	12.758%	$42.3181	$42.32	$42.30	$42.30
Purchase #6	$44.82	10.806%	$49.6632	$49.66	$49.65	$49.70
Purchase #7	$131.75	5.507%	$139.0055	$139.01	$139.00	$139.00
7 purchase totals =	$683.87		$744.1438	$744.15	$744.15	$744.20