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	$38.39	12.754%	$43.2863	$43.29	$43.30	$43.30
Purchase #2	$129.62	8.237%	$140.2968	$140.30	$140.30	$140.30
Purchase #3	$45.33	5.555%	$47.8481	$47.85	$47.85	$47.80
Purchase #4	$42.45	9.290%	$46.3936	$46.39	$46.40	$46.40
Purchase #5	$94.50	6.793%	$100.9194	$100.92	$100.90	$100.90
Purchase #6	$210.66	3.276%	$217.5612	$217.56	$217.55	$217.60
Purchase #7	$93.74	7.339%	$100.6196	$100.62	$100.60	$100.60
7 purchase totals =	$654.69		$696.9250	$696.93	$696.90	$696.90