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	$100.57	11.812%	$112.4493	$112.45	$112.45	$112.40
Purchase #2	$222.42	8.581%	$241.5059	$241.51	$241.50	$241.50
Purchase #3	$220.47	3.824%	$228.9008	$228.90	$228.90	$228.90
Purchase #4	$73.92	10.767%	$81.879	$81.88	$81.90	$81.90
Purchase #5	$219.87	13.186%	$248.8621	$248.86	$248.85	$248.90
Purchase #6	$183.97	11.683%	$205.4632	$205.46	$205.45	$205.50
Purchase #7	$172.75	3.800%	$179.3145	$179.31	$179.30	$179.30
7 purchase totals =	$1,193.97		$1,298.3748	$1,298.37	$1,298.35	$1,298.40