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	$180.66	13.869%	$205.7157	$205.72	$205.70	$205.70
Purchase #2	$177.25	8.126%	$191.6533	$191.65	$191.65	$191.70
Purchase #3	$77.92	4.414%	$81.3594	$81.36	$81.35	$81.40
Purchase #4	$32.27	6.249%	$34.2866	$34.29	$34.30	$34.30
Purchase #5	$54.94	3.434%	$56.8266	$56.83	$56.85	$56.80
Purchase #6	$78.95	13.478%	$89.5909	$89.59	$89.60	$89.60
Purchase #7	$26.42	5.173%	$27.7867	$27.79	$27.80	$27.80
7 purchase totals =	$628.41		$687.2192	$687.23	$687.25	$687.30