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	$106.87	4.682%	$111.8737	$111.87	$111.85	$111.90
Purchase #2	$136.80	4.764%	$143.3172	$143.32	$143.30	$143.30
Purchase #3	$233.69	13.193%	$264.5207	$264.52	$264.50	$264.50
Purchase #4	$231.82	6.373%	$246.5939	$246.59	$246.60	$246.60
Purchase #5	$180.45	3.638%	$187.0148	$187.01	$187.00	$187.00
Purchase #6	$78.96	5.638%	$83.4118	$83.41	$83.40	$83.40
Purchase #7	$20.57	10.660%	$22.7628	$22.76	$22.75	$22.80
7 purchase totals =	$989.16		$1,059.4949	$1,059.48	$1,059.40	$1,059.50