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	$61.59	10.778%	$68.2282	$68.23	$68.25	$68.20
Purchase #2	$70.48	9.210%	$76.9712	$76.97	$76.95	$77.00
Purchase #3	$124.44	12.844%	$140.4231	$140.42	$140.40	$140.40
Purchase #4	$94.78	5.655%	$100.1398	$100.14	$100.15	$100.10
Purchase #5	$101.94	9.452%	$111.5754	$111.58	$111.60	$111.60
Purchase #6	$205.94	8.562%	$223.5726	$223.57	$223.55	$223.60
Purchase #7	$144.57	11.771%	$161.5873	$161.59	$161.60	$161.60
7 purchase totals =	$803.74		$882.4976	$882.50	$882.50	$882.50