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	$47.61	10.593%	$52.6533	$52.65	$52.65	$52.70
Purchase #2	$104.80	11.507%	$116.8593	$116.86	$116.85	$116.90
Purchase #3	$56.94	11.672%	$63.586	$63.59	$63.60	$63.60
Purchase #4	$82.85	10.237%	$91.3314	$91.33	$91.35	$91.30
Purchase #5	$96.91	10.303%	$106.8946	$106.89	$106.90	$106.90
Purchase #6	$112.61	11.633%	$125.7099	$125.71	$125.70	$125.70
Purchase #7	$20.65	4.105%	$21.4977	$21.50	$21.50	$21.50
7 purchase totals =	$522.37		$578.5322	$578.53	$578.55	$578.60