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	$226.27	4.109%	$235.5674	$235.57	$235.55	$235.60
Purchase #2	$38.38	9.642%	$42.0806	$42.08	$42.10	$42.10
Purchase #3	$150.68	8.636%	$163.6927	$163.69	$163.70	$163.70
Purchase #4	$50.99	11.808%	$57.0109	$57.01	$57.00	$57.00
Purchase #5	$221.60	10.178%	$244.1544	$244.15	$244.15	$244.20
Purchase #6	$180.84	8.459%	$196.1373	$196.14	$196.15	$196.10
Purchase #7	$116.94	5.337%	$123.1811	$123.18	$123.20	$123.20
7 purchase totals =	$985.70		$1,061.8244	$1,061.82	$1,061.85	$1,061.90