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	$226.87	3.470%	$234.7424	$234.74	$234.75	$234.70
Purchase #2	$117.46	11.839%	$131.3661	$131.37	$131.35	$131.40
Purchase #3	$46.32	11.429%	$51.6139	$51.61	$51.60	$51.60
Purchase #4	$59.85	12.571%	$67.3737	$67.37	$67.35	$67.40
Purchase #5	$70.44	8.628%	$76.5176	$76.52	$76.50	$76.50
Purchase #6	$164.42	10.518%	$181.7137	$181.71	$181.70	$181.70
Purchase #7	$151.82	3.632%	$157.3341	$157.33	$157.35	$157.30
7 purchase totals =	$837.18		$900.6615	$900.65	$900.60	$900.60