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	$99.37	5.136%	$104.4736	$104.47	$104.45	$104.50
Purchase #2	$199.43	3.532%	$206.4739	$206.47	$206.45	$206.50
Purchase #3	$226.46	10.602%	$250.4693	$250.47	$250.45	$250.50
Purchase #4	$168.42	12.860%	$190.0788	$190.08	$190.10	$190.10
Purchase #5	$182.39	6.649%	$194.5171	$194.52	$194.50	$194.50
Purchase #6	$70.69	8.725%	$76.8577	$76.86	$76.85	$76.90
Purchase #7	$190.26	13.467%	$215.8823	$215.88	$215.90	$215.90
7 purchase totals =	$1,137.02		$1,238.7527	$1,238.75	$1,238.70	$1,238.90