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	$103.83	9.648%	$113.8475	$113.85	$113.85	$113.80
Purchase #2	$42.66	5.529%	$45.0187	$45.02	$45.00	$45.00
Purchase #3	$95.35	7.729%	$102.7196	$102.72	$102.70	$102.70
Purchase #4	$63.95	3.636%	$66.2752	$66.28	$66.30	$66.30
Purchase #5	$20.32	11.141%	$22.5839	$22.58	$22.60	$22.60
Purchase #6	$196.97	5.868%	$208.5282	$208.53	$208.55	$208.50
Purchase #7	$143.60	6.418%	$152.8162	$152.82	$152.80	$152.80
7 purchase totals =	$666.68		$711.7893	$711.80	$711.80	$711.70