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	$140.73	12.558%	$158.4029	$158.40	$158.40	$158.40
Purchase #2	$9.45	6.667%	$10.08	$10.08	$10.10	$10.10
Purchase #3	$226.72	10.108%	$249.6369	$249.64	$249.65	$249.60
Purchase #4	$202.37	10.417%	$223.4509	$223.45	$223.45	$223.50
Purchase #5	$166.83	4.492%	$174.324	$174.32	$174.30	$174.30
Purchase #6	$123.34	13.183%	$139.5999	$139.60	$139.60	$139.60
Purchase #7	$112.64	12.616%	$126.8507	$126.85	$126.85	$126.90
7 purchase totals =	$982.08		$1,082.3453	$1,082.34	$1,082.35	$1,082.40