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	$171.41	5.167%	$180.2668	$180.27	$180.25	$180.30
Purchase #2	$199.59	6.189%	$211.9426	$211.94	$211.95	$211.90
Purchase #3	$189.80	3.500%	$196.443	$196.44	$196.45	$196.40
Purchase #4	$141.95	5.736%	$150.0923	$150.09	$150.10	$150.10
Purchase #5	$230.82	11.177%	$256.6188	$256.62	$256.60	$256.60
Purchase #6	$38.86	5.685%	$41.0692	$41.07	$41.05	$41.10
Purchase #7	$33.89	13.860%	$38.5872	$38.59	$38.60	$38.60
7 purchase totals =	$1,006.32		$1,075.0199	$1,075.02	$1,075.00	$1,075.00