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	$63.70	10.790%	$70.5732	$70.57	$70.55	$70.60
Purchase #2	$199.34	13.724%	$226.6974	$226.70	$226.70	$226.70
Purchase #3	$77.51	10.479%	$85.6323	$85.63	$85.65	$85.60
Purchase #4	$72.63	7.493%	$78.0722	$78.07	$78.05	$78.10
Purchase #5	$125.95	6.805%	$134.5209	$134.52	$134.50	$134.50
Purchase #6	$235.86	8.497%	$255.901	$255.90	$255.90	$255.90
Purchase #7	$248.58	13.648%	$282.5062	$282.51	$282.50	$282.50
7 purchase totals =	$1,023.57		$1,133.9032	$1,133.90	$1,133.85	$1,133.90