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	$169.64	6.843%	$181.2485	$181.25	$181.25	$181.20
Purchase #2	$156.46	10.839%	$173.4187	$173.42	$173.40	$173.40
Purchase #3	$153.96	7.614%	$165.6825	$165.68	$165.70	$165.70
Purchase #4	$63.55	3.186%	$65.5747	$65.57	$65.55	$65.60
Purchase #5	$39.38	8.771%	$42.834	$42.83	$42.85	$42.80
Purchase #6	$154.48	13.189%	$174.8544	$174.85	$174.85	$174.90
Purchase #7	$160.90	9.755%	$176.5958	$176.60	$176.60	$176.60
7 purchase totals =	$898.37		$980.2086	$980.20	$980.20	$980.20