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	$69.46	4.786%	$72.7844	$72.78	$72.80	$72.80
Purchase #2	$83.50	10.153%	$91.9778	$91.98	$92.00	$92.00
Purchase #3	$54.75	13.201%	$61.9775	$61.98	$62.00	$62.00
Purchase #4	$47.78	8.678%	$51.9263	$51.93	$51.95	$51.90
Purchase #5	$87.58	13.356%	$99.2772	$99.28	$99.30	$99.30
Purchase #6	$184.72	5.112%	$194.1629	$194.16	$194.15	$194.20
Purchase #7	$51.87	9.528%	$56.8122	$56.81	$56.80	$56.80
7 purchase totals =	$579.66		$628.9183	$628.92	$629.00	$629.00