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	$206.94	9.451%	$226.4979	$226.50	$226.50	$226.50
Purchase #2	$117.89	13.131%	$133.3701	$133.37	$133.35	$133.40
Purchase #3	$110.43	12.330%	$124.046	$124.05	$124.05	$124.00
Purchase #4	$139.39	4.347%	$145.4493	$145.45	$145.45	$145.40
Purchase #5	$63.79	12.304%	$71.6387	$71.64	$71.65	$71.60
Purchase #6	$180.31	6.260%	$191.5974	$191.60	$191.60	$191.60
Purchase #7	$36.86	9.638%	$40.4126	$40.41	$40.40	$40.40
7 purchase totals =	$855.61		$933.0120	$933.02	$933.00	$932.90