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	$127.46	12.503%	$143.3963	$143.40	$143.40	$143.40
Purchase #2	$99.76	4.683%	$104.4318	$104.43	$104.45	$104.40
Purchase #3	$100.86	8.284%	$109.2152	$109.22	$109.20	$109.20
Purchase #4	$46.75	12.620%	$52.6499	$52.65	$52.65	$52.60
Purchase #5	$58.79	7.359%	$63.1164	$63.12	$63.10	$63.10
Purchase #6	$38.46	13.629%	$43.7017	$43.70	$43.70	$43.70
Purchase #7	$97.34	12.554%	$109.5601	$109.56	$109.55	$109.60
7 purchase totals =	$569.42		$626.0714	$626.08	$626.05	$626.00