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	$52.70	5.723%	$55.716	$55.72	$55.70	$55.70
Purchase #2	$5.42	12.724%	$6.1096	$6.11	$6.10	$6.10
Purchase #3	$78.93	13.533%	$89.6116	$89.61	$89.60	$89.60
Purchase #4	$97.33	4.374%	$101.5872	$101.59	$101.60	$101.60
Purchase #5	$29.86	4.233%	$31.124	$31.12	$31.10	$31.10
Purchase #6	$44.68	10.627%	$49.4281	$49.43	$49.45	$49.40
Purchase #7	$148.38	11.509%	$165.4571	$165.46	$165.45	$165.50
7 purchase totals =	$457.30		$499.0336	$499.04	$499.00	$499.00