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	$78.31	10.377%	$86.4362	$86.44	$86.45	$86.40
Purchase #2	$63.55	9.809%	$69.7836	$69.78	$69.80	$69.80
Purchase #3	$88.80	12.269%	$99.6949	$99.69	$99.70	$99.70
Purchase #4	$233.63	10.451%	$258.0467	$258.05	$258.05	$258.00
Purchase #5	$48.51	8.808%	$52.7828	$52.78	$52.80	$52.80
Purchase #6	$241.87	13.509%	$274.5442	$274.54	$274.55	$274.50
Purchase #7	$37.29	12.702%	$42.0266	$42.03	$42.05	$42.00
7 purchase totals =	$791.96		$883.3150	$883.31	$883.40	$883.20