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	$191.62	8.805%	$208.4921	$208.49	$208.50	$208.50
Purchase #2	$79.86	12.521%	$89.8593	$89.86	$89.85	$89.90
Purchase #3	$141.66	8.613%	$153.8612	$153.86	$153.85	$153.90
Purchase #4	$108.47	13.263%	$122.8564	$122.86	$122.85	$122.90
Purchase #5	$55.77	11.368%	$62.1099	$62.11	$62.10	$62.10
Purchase #6	$55.80	3.724%	$57.878	$57.88	$57.90	$57.90
Purchase #7	$79.32	5.128%	$83.3875	$83.39	$83.40	$83.40
7 purchase totals =	$712.50		$778.4444	$778.45	$778.45	$778.60