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	$194.80	12.671%	$219.4831	$219.48	$219.50	$219.50
Purchase #2	$196.75	8.514%	$213.5013	$213.50	$213.50	$213.50
Purchase #3	$154.49	3.280%	$159.5573	$159.56	$159.55	$159.60
Purchase #4	$19.56	9.144%	$21.3486	$21.35	$21.35	$21.30
Purchase #5	$172.87	9.248%	$188.857	$188.86	$188.85	$188.90
Purchase #6	$137.61	4.487%	$143.7846	$143.78	$143.80	$143.80
Purchase #7	$173.62	13.435%	$196.9458	$196.95	$196.95	$196.90
7 purchase totals =	$1,049.70		$1,143.4777	$1,143.48	$1,143.50	$1,143.50