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	$155.69	10.319%	$171.7557	$171.76	$171.75	$171.80
Purchase #2	$137.48	9.166%	$150.0814	$150.08	$150.10	$150.10
Purchase #3	$161.42	6.872%	$172.5128	$172.51	$172.50	$172.50
Purchase #4	$82.71	7.262%	$88.7164	$88.72	$88.70	$88.70
Purchase #5	$167.52	5.511%	$176.752	$176.75	$176.75	$176.80
Purchase #6	$139.76	8.864%	$152.1483	$152.15	$152.15	$152.10
Purchase #7	$19.54	9.830%	$21.4608	$21.46	$21.45	$21.50
7 purchase totals =	$864.12		$933.4274	$933.43	$933.40	$933.50