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	$144.67	9.490%	$158.3992	$158.40	$158.40	$158.40
Purchase #2	$98.81	10.195%	$108.8837	$108.88	$108.90	$108.90
Purchase #3	$215.41	3.286%	$222.4884	$222.49	$222.50	$222.50
Purchase #4	$117.90	12.412%	$132.5337	$132.53	$132.55	$132.50
Purchase #5	$56.43	9.572%	$61.8315	$61.83	$61.85	$61.80
Purchase #6	$114.44	6.705%	$122.1132	$122.11	$122.10	$122.10
Purchase #7	$144.36	4.701%	$151.1464	$151.15	$151.15	$151.10
7 purchase totals =	$892.02		$957.3961	$957.39	$957.45	$957.30