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	$52.76	9.636%	$57.844	$57.84	$57.85	$57.80
Purchase #2	$147.28	12.755%	$166.0656	$166.07	$166.05	$166.10
Purchase #3	$230.84	13.672%	$262.4004	$262.40	$262.40	$262.40
Purchase #4	$46.94	10.381%	$51.8128	$51.81	$51.80	$51.80
Purchase #5	$40.51	11.741%	$45.2663	$45.27	$45.25	$45.30
Purchase #6	$206.93	5.207%	$217.7048	$217.70	$217.70	$217.70
Purchase #7	$156.32	10.308%	$172.4335	$172.43	$172.45	$172.40
7 purchase totals =	$881.58		$973.5274	$973.52	$973.50	$973.50