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	$136.89	4.336%	$142.8256	$142.83	$142.85	$142.80
Purchase #2	$90.54	4.458%	$94.5763	$94.58	$94.60	$94.60
Purchase #3	$126.85	4.440%	$132.4821	$132.48	$132.50	$132.50
Purchase #4	$69.80	5.791%	$73.8421	$73.84	$73.85	$73.80
Purchase #5	$128.47	4.812%	$134.652	$134.65	$134.65	$134.70
Purchase #6	$164.35	11.175%	$182.7161	$182.72	$182.70	$182.70
Purchase #7	$230.29	12.341%	$258.7101	$258.71	$258.70	$258.70
7 purchase totals =	$947.19		$1,019.8043	$1,019.81	$1,019.85	$1,019.80