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	$217.85	3.185%	$224.7885	$224.79	$224.80	$224.80
Purchase #2	$200.46	7.497%	$215.4885	$215.49	$215.50	$215.50
Purchase #3	$147.52	8.789%	$160.4855	$160.49	$160.50	$160.50
Purchase #4	$8.42	11.256%	$9.3678	$9.37	$9.35	$9.40
Purchase #5	$150.86	11.472%	$168.1667	$168.17	$168.15	$168.20
Purchase #6	$149.72	11.542%	$167.0007	$167.00	$167.00	$167.00
Purchase #7	$95.31	10.664%	$105.4739	$105.47	$105.45	$105.50
7 purchase totals =	$970.14		$1,050.7716	$1,050.78	$1,050.75	$1,050.90