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	$76.72	5.678%	$81.0762	$81.08	$81.10	$81.10
Purchase #2	$243.53	9.509%	$266.6873	$266.69	$266.70	$266.70
Purchase #3	$93.90	4.861%	$98.4645	$98.46	$98.45	$98.50
Purchase #4	$153.95	7.712%	$165.8226	$165.82	$165.80	$165.80
Purchase #5	$237.54	7.667%	$255.7522	$255.75	$255.75	$255.80
Purchase #6	$88.46	6.528%	$94.2347	$94.23	$94.25	$94.20
Purchase #7	$105.32	13.811%	$119.8657	$119.87	$119.85	$119.90
7 purchase totals =	$999.42		$1,081.9032	$1,081.90	$1,081.90	$1,082.00