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	$250.41	5.357%	$263.8245	$263.82	$263.80	$263.80
Purchase #2	$143.88	5.181%	$151.3344	$151.33	$151.35	$151.30
Purchase #3	$156.59	3.561%	$162.1662	$162.17	$162.15	$162.20
Purchase #4	$193.53	13.739%	$220.1191	$220.12	$220.10	$220.10
Purchase #5	$5.85	10.262%	$6.4503	$6.45	$6.45	$6.50
Purchase #6	$174.93	3.119%	$180.3861	$180.39	$180.40	$180.40
Purchase #7	$225.65	13.723%	$256.6159	$256.62	$256.60	$256.60
7 purchase totals =	$1,150.84		$1,240.8965	$1,240.90	$1,240.85	$1,240.90