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	$31.28	5.756%	$33.0805	$33.08	$33.10	$33.10
Purchase #2	$13.99	3.543%	$14.4857	$14.49	$14.50	$14.50
Purchase #3	$39.30	11.681%	$43.8906	$43.89	$43.90	$43.90
Purchase #4	$164.64	4.795%	$172.5345	$172.53	$172.55	$172.50
Purchase #5	$182.77	3.829%	$189.7683	$189.77	$189.75	$189.80
Purchase #6	$75.86	9.422%	$83.0075	$83.01	$83.00	$83.00
Purchase #7	$114.92	6.873%	$122.8185	$122.82	$122.80	$122.80
7 purchase totals =	$622.76		$659.5856	$659.59	$659.60	$659.60