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	$105.42	10.488%	$116.4764	$116.48	$116.50	$116.50
Purchase #2	$172.28	7.874%	$185.8453	$185.85	$185.85	$185.80
Purchase #3	$158.64	13.314%	$179.7613	$179.76	$179.75	$179.80
Purchase #4	$9.31	10.864%	$10.3214	$10.32	$10.30	$10.30
Purchase #5	$200.57	8.556%	$217.7308	$217.73	$217.75	$217.70
Purchase #6	$52.74	6.649%	$56.2467	$56.25	$56.25	$56.20
Purchase #7	$89.73	8.282%	$97.1614	$97.16	$97.15	$97.20
7 purchase totals =	$788.69		$863.5433	$863.55	$863.55	$863.50