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	$147.42	7.317%	$158.2067	$158.21	$158.20	$158.20
Purchase #2	$102.69	5.742%	$108.5865	$108.59	$108.60	$108.60
Purchase #3	$160.77	6.384%	$171.0336	$171.03	$171.05	$171.00
Purchase #4	$117.61	11.393%	$131.0093	$131.01	$131.00	$131.00
Purchase #5	$99.26	3.536%	$102.7698	$102.77	$102.75	$102.80
Purchase #6	$18.91	10.256%	$20.8494	$20.85	$20.85	$20.80
Purchase #7	$57.47	10.657%	$63.5946	$63.59	$63.60	$63.60
7 purchase totals =	$704.13		$756.0499	$756.05	$756.05	$756.00