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	$98.93	12.590%	$111.3853	$111.39	$111.40	$111.40
Purchase #2	$41.39	12.836%	$46.7028	$46.70	$46.70	$46.70
Purchase #3	$111.56	9.264%	$121.8949	$121.89	$121.90	$121.90
Purchase #4	$143.68	6.814%	$153.4704	$153.47	$153.45	$153.50
Purchase #5	$186.67	6.274%	$198.3817	$198.38	$198.40	$198.40
Purchase #6	$73.76	11.724%	$82.4076	$82.41	$82.40	$82.40
Purchase #7	$37.82	10.237%	$41.6916	$41.69	$41.70	$41.70
7 purchase totals =	$693.81		$755.9343	$755.93	$755.95	$756.00