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	$114.39	11.538%	$127.5883	$127.59	$127.60	$127.60
Purchase #2	$208.45	8.698%	$226.581	$226.58	$226.60	$226.60
Purchase #3	$54.54	8.849%	$59.3662	$59.37	$59.35	$59.40
Purchase #4	$188.27	5.329%	$198.3029	$198.30	$198.30	$198.30
Purchase #5	$85.60	11.370%	$95.3327	$95.33	$95.35	$95.30
Purchase #6	$10.93	10.185%	$12.0432	$12.04	$12.05	$12.00
Purchase #7	$242.35	6.278%	$257.5647	$257.56	$257.55	$257.60
7 purchase totals =	$904.53		$976.7790	$976.77	$976.80	$976.80