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	$241.62	5.643%	$255.2546	$255.25	$255.25	$255.30
Purchase #2	$153.31	10.198%	$168.9446	$168.94	$168.95	$168.90
Purchase #3	$24.62	13.200%	$27.8698	$27.87	$27.85	$27.90
Purchase #4	$62.31	4.823%	$65.3152	$65.32	$65.30	$65.30
Purchase #5	$95.50	9.493%	$104.5658	$104.57	$104.55	$104.60
Purchase #6	$229.39	12.353%	$257.7265	$257.73	$257.75	$257.70
Purchase #7	$190.66	8.394%	$206.664	$206.66	$206.65	$206.70
7 purchase totals =	$997.41		$1,086.3405	$1,086.34	$1,086.30	$1,086.40