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	$224.60	13.796%	$255.5858	$255.59	$255.60	$255.60
Purchase #2	$192.92	3.490%	$199.6529	$199.65	$199.65	$199.70
Purchase #3	$48.97	11.496%	$54.5996	$54.60	$54.60	$54.60
Purchase #4	$48.76	13.426%	$55.3065	$55.31	$55.30	$55.30
Purchase #5	$239.39	8.281%	$259.2139	$259.21	$259.20	$259.20
Purchase #6	$100.76	12.176%	$113.0285	$113.03	$113.05	$113.00
Purchase #7	$179.83	3.863%	$186.7768	$186.78	$186.80	$186.80
7 purchase totals =	$1,035.23		$1,124.1640	$1,124.17	$1,124.20	$1,124.20