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	$235.52	8.180%	$254.7855	$254.79	$254.80	$254.80
Purchase #2	$70.94	4.105%	$73.8521	$73.85	$73.85	$73.90
Purchase #3	$55.84	13.479%	$63.3667	$63.37	$63.35	$63.40
Purchase #4	$47.42	8.658%	$51.5256	$51.53	$51.55	$51.50
Purchase #5	$75.46	13.810%	$85.881	$85.88	$85.90	$85.90
Purchase #6	$178.60	7.709%	$192.3683	$192.37	$192.35	$192.40
Purchase #7	$187.67	4.741%	$196.5674	$196.57	$196.55	$196.60
7 purchase totals =	$851.45		$918.3466	$918.36	$918.35	$918.50