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	$128.96	9.185%	$140.805	$140.81	$140.80	$140.80
Purchase #2	$90.38	6.253%	$96.0315	$96.03	$96.05	$96.00
Purchase #3	$107.46	13.609%	$122.0842	$122.08	$122.10	$122.10
Purchase #4	$69.60	3.503%	$72.0381	$72.04	$72.05	$72.00
Purchase #5	$217.53	11.184%	$241.8586	$241.86	$241.85	$241.90
Purchase #6	$55.85	7.246%	$59.8969	$59.90	$59.90	$59.90
Purchase #7	$176.41	13.285%	$199.8461	$199.85	$199.85	$199.80
7 purchase totals =	$846.19		$932.5604	$932.57	$932.60	$932.50