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	$143.83	10.188%	$158.4834	$158.48	$158.50	$158.50
Purchase #2	$148.32	9.465%	$162.3585	$162.36	$162.35	$162.40
Purchase #3	$222.94	6.310%	$237.0075	$237.01	$237.00	$237.00
Purchase #4	$94.82	11.528%	$105.7508	$105.75	$105.75	$105.80
Purchase #5	$55.99	12.279%	$62.865	$62.87	$62.85	$62.90
Purchase #6	$247.56	5.522%	$261.2303	$261.23	$261.25	$261.20
Purchase #7	$119.89	13.557%	$136.1435	$136.14	$136.15	$136.10
7 purchase totals =	$1,033.35		$1,123.8390	$1,123.84	$1,123.85	$1,123.90