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	$95.73	10.528%	$105.8085	$105.81	$105.80	$105.80
Purchase #2	$164.38	9.423%	$179.8695	$179.87	$179.85	$179.90
Purchase #3	$62.74	6.109%	$66.5728	$66.57	$66.55	$66.60
Purchase #4	$174.60	6.390%	$185.7569	$185.76	$185.75	$185.80
Purchase #5	$206.93	10.584%	$228.8315	$228.83	$228.85	$228.80
Purchase #6	$67.35	13.620%	$76.5231	$76.52	$76.50	$76.50
Purchase #7	$10.53	13.838%	$11.9871	$11.99	$12.00	$12.00
7 purchase totals =	$782.26		$855.3494	$855.35	$855.30	$855.40