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	$109.89	8.811%	$119.5724	$119.57	$119.55	$119.60
Purchase #2	$141.72	13.289%	$160.5532	$160.55	$160.55	$160.60
Purchase #3	$34.58	8.723%	$37.5964	$37.60	$37.60	$37.60
Purchase #4	$131.96	5.618%	$139.3735	$139.37	$139.35	$139.40
Purchase #5	$199.83	10.455%	$220.7222	$220.72	$220.70	$220.70
Purchase #6	$184.96	5.783%	$195.6562	$195.66	$195.65	$195.70
Purchase #7	$146.46	8.256%	$158.5517	$158.55	$158.55	$158.60
7 purchase totals =	$949.40		$1,032.0256	$1,032.02	$1,031.95	$1,032.20