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	$48.30	8.593%	$52.4504	$52.45	$52.45	$52.50
Purchase #2	$55.44	6.643%	$59.1229	$59.12	$59.10	$59.10
Purchase #3	$83.89	13.295%	$95.0432	$95.04	$95.05	$95.00
Purchase #4	$106.30	7.567%	$114.3437	$114.34	$114.35	$114.30
Purchase #5	$224.89	9.276%	$245.7508	$245.75	$245.75	$245.80
Purchase #6	$28.51	3.798%	$29.5928	$29.59	$29.60	$29.60
Purchase #7	$224.78	10.230%	$247.775	$247.78	$247.80	$247.80
7 purchase totals =	$772.11		$844.0788	$844.07	$844.10	$844.10