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	$146.40	9.509%	$160.3212	$160.32	$160.30	$160.30
Purchase #2	$63.35	11.401%	$70.5725	$70.57	$70.55	$70.60
Purchase #3	$40.93	13.844%	$46.5963	$46.60	$46.60	$46.60
Purchase #4	$144.59	8.867%	$157.4108	$157.41	$157.40	$157.40
Purchase #5	$128.42	12.855%	$144.9284	$144.93	$144.95	$144.90
Purchase #6	$73.55	12.639%	$82.846	$82.85	$82.85	$82.80
Purchase #7	$167.31	7.745%	$180.2682	$180.27	$180.25	$180.30
7 purchase totals =	$764.55		$842.9434	$842.95	$842.90	$842.90