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	$217.56	3.346%	$224.8396	$224.84	$224.85	$224.80
Purchase #2	$85.68	11.422%	$95.4664	$95.47	$95.45	$95.50
Purchase #3	$94.46	11.670%	$105.4835	$105.48	$105.50	$105.50
Purchase #4	$195.64	6.823%	$208.9885	$208.99	$209.00	$209.00
Purchase #5	$117.78	11.528%	$131.3577	$131.36	$131.35	$131.40
Purchase #6	$48.50	6.314%	$51.5623	$51.56	$51.55	$51.60
Purchase #7	$166.51	4.855%	$174.5941	$174.59	$174.60	$174.60
7 purchase totals =	$926.13		$992.2921	$992.29	$992.30	$992.40