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	$220.71	11.477%	$246.0409	$246.04	$246.05	$246.00
Purchase #2	$98.58	12.383%	$110.7872	$110.79	$110.80	$110.80
Purchase #3	$247.67	5.224%	$260.6083	$260.61	$260.60	$260.60
Purchase #4	$225.57	13.124%	$255.1738	$255.17	$255.15	$255.20
Purchase #5	$90.82	10.750%	$100.5832	$100.58	$100.60	$100.60
Purchase #6	$109.92	12.590%	$123.7589	$123.76	$123.75	$123.80
Purchase #7	$148.80	13.525%	$168.9252	$168.93	$168.95	$168.90
7 purchase totals =	$1,142.07		$1,265.8775	$1,265.88	$1,265.90	$1,265.90