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	$154.88	10.606%	$171.3066	$171.31	$171.30	$171.30
Purchase #2	$114.43	3.157%	$118.0426	$118.04	$118.05	$118.00
Purchase #3	$10.32	5.160%	$10.8525	$10.85	$10.85	$10.90
Purchase #4	$59.94	10.699%	$66.353	$66.35	$66.35	$66.40
Purchase #5	$247.65	10.394%	$273.3907	$273.39	$273.40	$273.40
Purchase #6	$65.86	13.448%	$74.7169	$74.72	$74.70	$74.70
Purchase #7	$9.83	10.763%	$10.888	$10.89	$10.90	$10.90
7 purchase totals =	$662.91		$725.5503	$725.55	$725.55	$725.60