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	$190.38	5.301%	$200.472	$200.47	$200.45	$200.50
Purchase #2	$85.43	7.797%	$92.091	$92.09	$92.10	$92.10
Purchase #3	$65.81	10.115%	$72.4667	$72.47	$72.45	$72.50
Purchase #4	$17.59	8.256%	$19.0422	$19.04	$19.05	$19.00
Purchase #5	$239.60	9.272%	$261.8157	$261.82	$261.80	$261.80
Purchase #6	$164.40	8.306%	$178.0551	$178.06	$178.05	$178.10
Purchase #7	$117.28	11.267%	$130.4939	$130.49	$130.50	$130.50
7 purchase totals =	$880.49		$954.4366	$954.44	$954.40	$954.50