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	$60.52	7.173%	$64.8611	$64.86	$64.85	$64.90
Purchase #2	$5.29	10.748%	$5.8586	$5.86	$5.85	$5.90
Purchase #3	$85.72	5.187%	$90.1663	$90.17	$90.15	$90.20
Purchase #4	$79.38	4.357%	$82.8386	$82.84	$82.85	$82.80
Purchase #5	$143.44	9.620%	$157.2389	$157.24	$157.25	$157.20
Purchase #6	$104.63	3.634%	$108.4323	$108.43	$108.45	$108.40
Purchase #7	$225.66	9.662%	$247.4633	$247.46	$247.45	$247.50
7 purchase totals =	$704.64		$756.8591	$756.86	$756.85	$756.90