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	$131.47	9.520%	$143.9859	$143.99	$144.00	$144.00
Purchase #2	$82.61	8.788%	$89.8698	$89.87	$89.85	$89.90
Purchase #3	$108.78	10.757%	$120.4815	$120.48	$120.50	$120.50
Purchase #4	$103.51	10.820%	$114.7098	$114.71	$114.70	$114.70
Purchase #5	$26.77	13.147%	$30.2895	$30.29	$30.30	$30.30
Purchase #6	$20.73	9.791%	$22.7597	$22.76	$22.75	$22.80
Purchase #7	$169.43	10.857%	$187.825	$187.83	$187.85	$187.80
7 purchase totals =	$643.30		$709.9212	$709.93	$709.95	$710.00