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	$90.38	3.466%	$93.5126	$93.51	$93.50	$93.50
Purchase #2	$91.70	9.398%	$100.318	$100.32	$100.30	$100.30
Purchase #3	$119.46	10.743%	$132.2936	$132.29	$132.30	$132.30
Purchase #4	$66.99	9.714%	$73.4974	$73.50	$73.50	$73.50
Purchase #5	$165.59	11.260%	$184.2354	$184.24	$184.25	$184.20
Purchase #6	$128.89	8.405%	$139.7232	$139.72	$139.70	$139.70
Purchase #7	$18.84	12.363%	$21.1692	$21.17	$21.15	$21.20
7 purchase totals =	$681.85		$744.7494	$744.75	$744.70	$744.70