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	$37.53	10.452%	$41.4526	$41.45	$41.45	$41.50
Purchase #2	$218.80	5.474%	$230.7771	$230.78	$230.80	$230.80
Purchase #3	$174.80	4.382%	$182.4597	$182.46	$182.45	$182.50
Purchase #4	$132.41	6.845%	$141.4735	$141.47	$141.45	$141.50
Purchase #5	$191.77	3.455%	$198.3957	$198.40	$198.40	$198.40
Purchase #6	$208.89	12.718%	$235.4566	$235.46	$235.45	$235.50
Purchase #7	$141.80	6.405%	$150.8823	$150.88	$150.90	$150.90
7 purchase totals =	$1,106.00		$1,180.8975	$1,180.90	$1,180.90	$1,181.10