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	$59.29	8.853%	$64.5389	$64.54	$64.55	$64.50
Purchase #2	$114.43	3.116%	$117.9956	$118.00	$118.00	$118.00
Purchase #3	$99.94	11.728%	$111.661	$111.66	$111.65	$111.70
Purchase #4	$84.72	5.668%	$89.5219	$89.52	$89.50	$89.50
Purchase #5	$139.32	3.239%	$143.8326	$143.83	$143.85	$143.80
Purchase #6	$161.93	4.125%	$168.6096	$168.61	$168.60	$168.60
Purchase #7	$126.65	10.760%	$140.2775	$140.28	$140.30	$140.30
7 purchase totals =	$786.28		$836.4371	$836.44	$836.45	$836.40