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	$57.50	13.462%	$65.2407	$65.24	$65.25	$65.20
Purchase #2	$168.61	9.672%	$184.918	$184.92	$184.90	$184.90
Purchase #3	$138.74	5.137%	$145.8671	$145.87	$145.85	$145.90
Purchase #4	$72.81	10.466%	$80.4303	$80.43	$80.45	$80.40
Purchase #5	$243.28	13.221%	$275.444	$275.44	$275.45	$275.40
Purchase #6	$141.96	6.705%	$151.4784	$151.48	$151.50	$151.50
Purchase #7	$59.59	6.847%	$63.6701	$63.67	$63.65	$63.70
7 purchase totals =	$882.49		$967.0486	$967.05	$967.05	$967.00