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	$231.41	10.223%	$255.067	$255.07	$255.05	$255.10
Purchase #2	$172.37	10.473%	$190.4223	$190.42	$190.40	$190.40
Purchase #3	$21.46	12.254%	$24.0897	$24.09	$24.10	$24.10
Purchase #4	$137.78	12.223%	$154.6208	$154.62	$154.60	$154.60
Purchase #5	$75.98	12.838%	$85.7343	$85.73	$85.75	$85.70
Purchase #6	$123.62	6.334%	$131.4501	$131.45	$131.45	$131.50
Purchase #7	$34.91	3.726%	$36.2107	$36.21	$36.20	$36.20
7 purchase totals =	$797.53		$877.5949	$877.59	$877.55	$877.60