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	$83.63	10.444%	$92.3643	$92.36	$92.35	$92.40
Purchase #2	$99.81	13.780%	$113.5638	$113.56	$113.55	$113.60
Purchase #3	$109.69	9.455%	$120.0612	$120.06	$120.05	$120.10
Purchase #4	$13.75	13.236%	$15.57	$15.57	$15.55	$15.60
Purchase #5	$80.70	6.527%	$85.9673	$85.97	$85.95	$86.00
Purchase #6	$63.42	3.452%	$65.6093	$65.61	$65.60	$65.60
Purchase #7	$225.48	13.200%	$255.2434	$255.24	$255.25	$255.20
7 purchase totals =	$676.48		$748.3793	$748.37	$748.30	$748.50