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	$113.30	4.609%	$118.522	$118.52	$118.50	$118.50
Purchase #2	$104.53	13.338%	$118.4722	$118.47	$118.45	$118.50
Purchase #3	$176.44	6.466%	$187.8486	$187.85	$187.85	$187.80
Purchase #4	$103.68	6.641%	$110.5654	$110.57	$110.55	$110.60
Purchase #5	$205.81	9.616%	$225.6007	$225.60	$225.60	$225.60
Purchase #6	$242.53	3.209%	$250.3128	$250.31	$250.30	$250.30
Purchase #7	$78.54	12.767%	$88.5672	$88.57	$88.55	$88.60
7 purchase totals =	$1,024.83		$1,099.8889	$1,099.89	$1,099.80	$1,099.90