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	$207.32	11.422%	$231.0001	$231.00	$231.00	$231.00
Purchase #2	$85.37	11.838%	$95.4761	$95.48	$95.50	$95.50
Purchase #3	$164.96	5.742%	$174.432	$174.43	$174.45	$174.40
Purchase #4	$187.46	9.808%	$205.8461	$205.85	$205.85	$205.80
Purchase #5	$150.80	5.344%	$158.8588	$158.86	$158.85	$158.90
Purchase #6	$152.47	13.318%	$172.776	$172.78	$172.80	$172.80
Purchase #7	$217.28	6.709%	$231.8573	$231.86	$231.85	$231.90
7 purchase totals =	$1,165.66		$1,270.2464	$1,270.26	$1,270.30	$1,270.30