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	$67.38	4.691%	$70.5408	$70.54	$70.55	$70.50
Purchase #2	$120.51	5.699%	$127.3779	$127.38	$127.40	$127.40
Purchase #3	$177.54	4.606%	$185.7175	$185.72	$185.70	$185.70
Purchase #4	$69.87	4.252%	$72.8409	$72.84	$72.85	$72.80
Purchase #5	$87.89	7.853%	$94.792	$94.79	$94.80	$94.80
Purchase #6	$169.94	13.103%	$192.2072	$192.21	$192.20	$192.20
Purchase #7	$203.72	13.789%	$231.811	$231.81	$231.80	$231.80
7 purchase totals =	$896.85		$975.2873	$975.29	$975.30	$975.20