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	$204.89	8.706%	$222.7277	$222.73	$222.75	$222.70
Purchase #2	$94.31	10.685%	$104.387	$104.39	$104.40	$104.40
Purchase #3	$22.67	12.509%	$25.5058	$25.51	$25.50	$25.50
Purchase #4	$31.85	10.578%	$35.2191	$35.22	$35.20	$35.20
Purchase #5	$130.91	10.469%	$144.615	$144.62	$144.60	$144.60
Purchase #6	$152.52	13.301%	$172.8067	$172.81	$172.80	$172.80
Purchase #7	$228.97	8.667%	$248.8148	$248.81	$248.80	$248.80
7 purchase totals =	$866.12		$954.0761	$954.09	$954.05	$954.00