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	$98.84	10.367%	$109.0867	$109.09	$109.10	$109.10
Purchase #2	$94.76	9.645%	$103.8996	$103.90	$103.90	$103.90
Purchase #3	$100.29	3.404%	$103.7039	$103.70	$103.70	$103.70
Purchase #4	$119.36	10.710%	$132.1435	$132.14	$132.15	$132.10
Purchase #5	$63.46	4.625%	$66.395	$66.40	$66.40	$66.40
Purchase #6	$231.78	6.202%	$246.155	$246.16	$246.15	$246.20
Purchase #7	$69.44	3.838%	$72.1051	$72.11	$72.10	$72.10
7 purchase totals =	$777.93		$833.4888	$833.50	$833.50	$833.50