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	$50.64	7.487%	$54.4314	$54.43	$54.45	$54.40
Purchase #2	$101.80	7.523%	$109.4584	$109.46	$109.45	$109.50
Purchase #3	$74.36	10.322%	$82.0354	$82.04	$82.05	$82.00
Purchase #4	$98.44	10.804%	$109.0755	$109.08	$109.10	$109.10
Purchase #5	$205.55	7.557%	$221.0834	$221.08	$221.10	$221.10
Purchase #6	$152.37	4.151%	$158.6949	$158.69	$158.70	$158.70
Purchase #7	$139.68	3.310%	$144.3034	$144.30	$144.30	$144.30
7 purchase totals =	$822.84		$879.0824	$879.08	$879.15	$879.10