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	$16.95	3.648%	$17.5683	$17.57	$17.55	$17.60
Purchase #2	$150.58	10.339%	$166.1485	$166.15	$166.15	$166.10
Purchase #3	$49.64	4.530%	$51.8887	$51.89	$51.90	$51.90
Purchase #4	$209.79	10.399%	$231.6061	$231.61	$231.60	$231.60
Purchase #5	$145.29	7.360%	$155.9833	$155.98	$156.00	$156.00
Purchase #6	$222.90	3.807%	$231.3858	$231.39	$231.40	$231.40
Purchase #7	$204.52	5.244%	$215.245	$215.25	$215.25	$215.20
7 purchase totals =	$999.67		$1,069.8257	$1,069.84	$1,069.85	$1,069.80