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	$169.57	11.843%	$189.6522	$189.65	$189.65	$189.70
Purchase #2	$59.54	10.674%	$65.8953	$65.90	$65.90	$65.90
Purchase #3	$239.39	13.319%	$271.2744	$271.27	$271.25	$271.30
Purchase #4	$125.51	4.757%	$131.4805	$131.48	$131.50	$131.50
Purchase #5	$78.67	12.780%	$88.724	$88.72	$88.70	$88.70
Purchase #6	$154.51	12.258%	$173.4498	$173.45	$173.45	$173.40
Purchase #7	$40.48	9.838%	$44.4624	$44.46	$44.45	$44.50
7 purchase totals =	$867.67		$964.9386	$964.93	$964.90	$965.00