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	$218.85	7.102%	$234.3927	$234.39	$234.40	$234.40
Purchase #2	$13.56	12.212%	$15.2159	$15.22	$15.20	$15.20
Purchase #3	$101.98	6.269%	$108.3731	$108.37	$108.35	$108.40
Purchase #4	$125.61	10.395%	$138.6672	$138.67	$138.65	$138.70
Purchase #5	$37.81	3.815%	$39.2525	$39.25	$39.25	$39.30
Purchase #6	$69.82	3.839%	$72.5004	$72.50	$72.50	$72.50
Purchase #7	$108.27	13.700%	$123.103	$123.10	$123.10	$123.10
7 purchase totals =	$675.90		$731.5048	$731.50	$731.45	$731.60