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	$85.30	11.689%	$95.2707	$95.27	$95.25	$95.30
Purchase #2	$82.34	4.157%	$85.7629	$85.76	$85.75	$85.80
Purchase #3	$134.84	9.479%	$147.6215	$147.62	$147.60	$147.60
Purchase #4	$111.31	11.250%	$123.8324	$123.83	$123.85	$123.80
Purchase #5	$90.52	5.471%	$95.4723	$95.47	$95.45	$95.50
Purchase #6	$49.92	3.486%	$51.6602	$51.66	$51.65	$51.70
Purchase #7	$111.54	9.371%	$121.9924	$121.99	$122.00	$122.00
7 purchase totals =	$665.77		$721.6124	$721.60	$721.55	$721.70