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	$93.45	12.317%	$104.9602	$104.96	$104.95	$105.00
Purchase #2	$153.60	13.538%	$174.3944	$174.39	$174.40	$174.40
Purchase #3	$148.60	4.708%	$155.5961	$155.60	$155.60	$155.60
Purchase #4	$50.59	11.816%	$56.5677	$56.57	$56.55	$56.60
Purchase #5	$117.44	3.765%	$121.8616	$121.86	$121.85	$121.90
Purchase #6	$19.50	11.819%	$21.8047	$21.80	$21.80	$21.80
Purchase #7	$102.66	8.577%	$111.4651	$111.47	$111.45	$111.50
7 purchase totals =	$685.84		$746.6498	$746.65	$746.60	$746.80