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	$126.35	13.755%	$143.7294	$143.73	$143.75	$143.70
Purchase #2	$160.60	11.742%	$179.4577	$179.46	$179.45	$179.50
Purchase #3	$166.42	3.472%	$172.1981	$172.20	$172.20	$172.20
Purchase #4	$171.84	10.772%	$190.3506	$190.35	$190.35	$190.40
Purchase #5	$248.25	13.796%	$282.4986	$282.50	$282.50	$282.50
Purchase #6	$95.83	7.756%	$103.2626	$103.26	$103.25	$103.30
Purchase #7	$56.58	7.416%	$60.776	$60.78	$60.80	$60.80
7 purchase totals =	$1,025.87		$1,132.2730	$1,132.28	$1,132.30	$1,132.40