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	$230.81	3.834%	$239.6593	$239.66	$239.65	$239.70
Purchase #2	$98.60	3.705%	$102.2531	$102.25	$102.25	$102.30
Purchase #3	$143.85	11.648%	$160.6056	$160.61	$160.60	$160.60
Purchase #4	$246.48	3.858%	$255.9892	$255.99	$256.00	$256.00
Purchase #5	$78.79	4.863%	$82.6216	$82.62	$82.60	$82.60
Purchase #6	$60.52	10.809%	$67.0616	$67.06	$67.05	$67.10
Purchase #7	$52.70	12.409%	$59.2395	$59.24	$59.25	$59.20
7 purchase totals =	$911.75		$967.4299	$967.43	$967.40	$967.50