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	$157.37	9.586%	$172.4555	$172.46	$172.45	$172.50
Purchase #2	$31.56	9.460%	$34.5456	$34.55	$34.55	$34.50
Purchase #3	$219.48	13.463%	$249.0286	$249.03	$249.05	$249.00
Purchase #4	$153.57	5.128%	$161.4451	$161.45	$161.45	$161.40
Purchase #5	$61.25	10.658%	$67.778	$67.78	$67.80	$67.80
Purchase #6	$141.44	9.681%	$155.1328	$155.13	$155.15	$155.10
Purchase #7	$102.72	8.615%	$111.5693	$111.57	$111.55	$111.60
7 purchase totals =	$867.39		$951.9549	$951.97	$952.00	$951.90