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	$221.41	9.284%	$241.9657	$241.97	$241.95	$242.00
Purchase #2	$109.48	8.581%	$118.8745	$118.87	$118.85	$118.90
Purchase #3	$170.26	11.682%	$190.1498	$190.15	$190.15	$190.10
Purchase #4	$117.81	11.843%	$131.7622	$131.76	$131.75	$131.80
Purchase #5	$47.78	7.305%	$51.2703	$51.27	$51.25	$51.30
Purchase #6	$185.50	12.752%	$209.155	$209.16	$209.15	$209.20
Purchase #7	$112.79	9.219%	$123.1881	$123.19	$123.20	$123.20
7 purchase totals =	$965.03		$1,066.3656	$1,066.37	$1,066.30	$1,066.50