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	$61.78	12.686%	$69.6174	$69.62	$69.60	$69.60
Purchase #2	$247.91	9.470%	$271.3871	$271.39	$271.40	$271.40
Purchase #3	$25.80	6.617%	$27.5072	$27.51	$27.50	$27.50
Purchase #4	$167.43	3.210%	$172.8045	$172.80	$172.80	$172.80
Purchase #5	$55.80	6.158%	$59.2362	$59.24	$59.25	$59.20
Purchase #6	$112.97	4.582%	$118.1463	$118.15	$118.15	$118.10
Purchase #7	$163.89	7.831%	$176.7242	$176.72	$176.70	$176.70
7 purchase totals =	$835.58		$895.4229	$895.43	$895.40	$895.30