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	$57.72	5.264%	$60.7584	$60.76	$60.75	$60.80
Purchase #2	$207.46	12.575%	$233.5481	$233.55	$233.55	$233.50
Purchase #3	$72.61	10.871%	$80.5034	$80.50	$80.50	$80.50
Purchase #4	$228.60	12.138%	$256.3475	$256.35	$256.35	$256.30
Purchase #5	$32.58	3.430%	$33.6975	$33.70	$33.70	$33.70
Purchase #6	$108.75	6.738%	$116.0776	$116.08	$116.10	$116.10
Purchase #7	$235.80	10.505%	$260.5708	$260.57	$260.55	$260.60
7 purchase totals =	$943.52		$1,041.5033	$1,041.51	$1,041.50	$1,041.50