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	$138.59	6.714%	$147.8949	$147.89	$147.90	$147.90
Purchase #2	$47.53	9.609%	$52.0972	$52.10	$52.10	$52.10
Purchase #3	$225.88	13.400%	$256.1479	$256.15	$256.15	$256.10
Purchase #4	$123.67	7.298%	$132.6954	$132.70	$132.70	$132.70
Purchase #5	$184.28	6.738%	$196.6968	$196.70	$196.70	$196.70
Purchase #6	$238.92	7.357%	$256.4973	$256.50	$256.50	$256.50
Purchase #7	$73.79	9.210%	$80.5861	$80.59	$80.60	$80.60
7 purchase totals =	$1,032.66		$1,122.6156	$1,122.63	$1,122.65	$1,122.60