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	$95.33	3.709%	$98.8658	$98.87	$98.85	$98.90
Purchase #2	$247.65	13.390%	$280.8103	$280.81	$280.80	$280.80
Purchase #3	$190.58	5.863%	$201.7537	$201.75	$201.75	$201.80
Purchase #4	$52.61	5.504%	$55.5057	$55.51	$55.50	$55.50
Purchase #5	$34.86	6.619%	$37.1674	$37.17	$37.15	$37.20
Purchase #6	$98.53	13.170%	$111.5064	$111.51	$111.50	$111.50
Purchase #7	$92.87	3.673%	$96.2811	$96.28	$96.30	$96.30
7 purchase totals =	$812.43		$881.8904	$881.90	$881.85	$882.00