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	$44.53	11.873%	$49.817	$49.82	$49.80	$49.80
Purchase #2	$50.65	3.620%	$52.4835	$52.48	$52.50	$52.50
Purchase #3	$24.27	12.813%	$27.3797	$27.38	$27.40	$27.40
Purchase #4	$196.30	8.857%	$213.6863	$213.69	$213.70	$213.70
Purchase #5	$54.98	13.487%	$62.3952	$62.40	$62.40	$62.40
Purchase #6	$30.96	8.619%	$33.6284	$33.63	$33.65	$33.60
Purchase #7	$38.45	4.380%	$40.1341	$40.13	$40.15	$40.10
7 purchase totals =	$440.14		$479.5242	$479.53	$479.60	$479.50