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	$200.58	7.389%	$215.4009	$215.40	$215.40	$215.40
Purchase #2	$48.53	8.240%	$52.5289	$52.53	$52.55	$52.50
Purchase #3	$15.41	4.427%	$16.0922	$16.09	$16.10	$16.10
Purchase #4	$80.59	13.311%	$91.3173	$91.32	$91.30	$91.30
Purchase #5	$73.85	6.342%	$78.5336	$78.53	$78.55	$78.50
Purchase #6	$90.93	12.653%	$102.4354	$102.44	$102.45	$102.40
Purchase #7	$120.82	5.381%	$127.3213	$127.32	$127.30	$127.30
7 purchase totals =	$630.71		$683.6296	$683.63	$683.65	$683.50