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	$36.82	13.796%	$41.8997	$41.90	$41.90	$41.90
Purchase #2	$62.80	13.389%	$71.2083	$71.21	$71.20	$71.20
Purchase #3	$63.50	4.650%	$66.4528	$66.45	$66.45	$66.50
Purchase #4	$51.31	6.761%	$54.7791	$54.78	$54.80	$54.80
Purchase #5	$92.89	8.254%	$100.5571	$100.56	$100.55	$100.60
Purchase #6	$75.88	9.810%	$83.3238	$83.32	$83.30	$83.30
Purchase #7	$198.42	5.527%	$209.3867	$209.39	$209.40	$209.40
7 purchase totals =	$581.62		$627.6075	$627.61	$627.60	$627.70