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	$66.77	8.170%	$72.2251	$72.23	$72.25	$72.20
Purchase #2	$32.97	4.732%	$34.5301	$34.53	$34.55	$34.50
Purchase #3	$59.88	11.211%	$66.5931	$66.59	$66.60	$66.60
Purchase #4	$199.33	3.639%	$206.5836	$206.58	$206.60	$206.60
Purchase #5	$27.85	6.442%	$29.6441	$29.64	$29.65	$29.60
Purchase #6	$164.57	12.630%	$185.3552	$185.36	$185.35	$185.40
Purchase #7	$100.95	10.406%	$111.4549	$111.45	$111.45	$111.50
7 purchase totals =	$652.32		$706.3861	$706.38	$706.45	$706.40