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	$140.65	10.849%	$155.9091	$155.91	$155.90	$155.90
Purchase #2	$134.62	13.469%	$152.752	$152.75	$152.75	$152.80
Purchase #3	$217.49	6.579%	$231.7987	$231.80	$231.80	$231.80
Purchase #4	$77.88	4.526%	$81.4048	$81.40	$81.40	$81.40
Purchase #5	$164.96	11.274%	$183.5576	$183.56	$183.55	$183.60
Purchase #6	$94.66	6.273%	$100.598	$100.60	$100.60	$100.60
Purchase #7	$187.55	3.557%	$194.2212	$194.22	$194.20	$194.20
7 purchase totals =	$1,017.81		$1,100.2414	$1,100.24	$1,100.20	$1,100.30