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	$213.35	6.601%	$227.4332	$227.43	$227.45	$227.40
Purchase #2	$57.94	8.475%	$62.8504	$62.85	$62.85	$62.90
Purchase #3	$6.85	10.309%	$7.5562	$7.56	$7.55	$7.60
Purchase #4	$86.78	3.360%	$89.6958	$89.70	$89.70	$89.70
Purchase #5	$205.96	4.705%	$215.6504	$215.65	$215.65	$215.70
Purchase #6	$70.88	13.617%	$80.5317	$80.53	$80.55	$80.50
Purchase #7	$38.89	11.567%	$43.3884	$43.39	$43.40	$43.40
7 purchase totals =	$680.65		$727.1061	$727.11	$727.15	$727.20