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	$95.66	10.381%	$105.5905	$105.59	$105.60	$105.60
Purchase #2	$55.57	11.596%	$62.0139	$62.01	$62.00	$62.00
Purchase #3	$82.75	9.647%	$90.7329	$90.73	$90.75	$90.70
Purchase #4	$103.75	3.782%	$107.6738	$107.67	$107.65	$107.70
Purchase #5	$190.26	4.187%	$198.2262	$198.23	$198.25	$198.20
Purchase #6	$75.83	8.462%	$82.2467	$82.25	$82.25	$82.20
Purchase #7	$250.71	7.587%	$269.7314	$269.73	$269.75	$269.70
7 purchase totals =	$854.53		$916.2154	$916.21	$916.25	$916.10