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	$116.93	9.609%	$128.1658	$128.17	$128.15	$128.20
Purchase #2	$68.45	5.300%	$72.0779	$72.08	$72.10	$72.10
Purchase #3	$158.96	6.619%	$169.4816	$169.48	$169.50	$169.50
Purchase #4	$51.74	11.108%	$57.4873	$57.49	$57.50	$57.50
Purchase #5	$17.57	10.236%	$19.3685	$19.37	$19.35	$19.40
Purchase #6	$132.53	4.650%	$138.6926	$138.69	$138.70	$138.70
Purchase #7	$78.56	10.514%	$86.8198	$86.82	$86.80	$86.80
7 purchase totals =	$624.74		$672.0935	$672.10	$672.10	$672.20