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	$214.63	4.727%	$224.7756	$224.78	$224.80	$224.80
Purchase #2	$13.82	8.656%	$15.0163	$15.02	$15.00	$15.00
Purchase #3	$143.66	6.382%	$152.8284	$152.83	$152.85	$152.80
Purchase #4	$247.37	13.275%	$280.2084	$280.21	$280.20	$280.20
Purchase #5	$111.70	13.165%	$126.4053	$126.41	$126.40	$126.40
Purchase #6	$129.46	10.782%	$143.4184	$143.42	$143.40	$143.40
Purchase #7	$166.52	10.855%	$184.5957	$184.60	$184.60	$184.60
7 purchase totals =	$1,027.16		$1,127.2481	$1,127.27	$1,127.25	$1,127.20