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	$143.79	10.323%	$158.6334	$158.63	$158.65	$158.60
Purchase #2	$167.47	10.522%	$185.0912	$185.09	$185.10	$185.10
Purchase #3	$83.83	5.826%	$88.7139	$88.71	$88.70	$88.70
Purchase #4	$220.99	5.383%	$232.8859	$232.89	$232.90	$232.90
Purchase #5	$7.33	8.310%	$7.9391	$7.94	$7.95	$7.90
Purchase #6	$186.98	11.539%	$208.5556	$208.56	$208.55	$208.60
Purchase #7	$201.64	7.868%	$217.505	$217.51	$217.50	$217.50
7 purchase totals =	$1,012.03		$1,099.3241	$1,099.33	$1,099.35	$1,099.30