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	$5.31	6.189%	$5.6386	$5.64	$5.65	$5.60
Purchase #2	$75.51	3.509%	$78.1596	$78.16	$78.15	$78.20
Purchase #3	$35.87	4.149%	$37.3582	$37.36	$37.35	$37.40
Purchase #4	$220.83	9.535%	$241.8861	$241.89	$241.90	$241.90
Purchase #5	$184.98	11.712%	$206.6449	$206.64	$206.65	$206.60
Purchase #6	$73.95	6.410%	$78.6902	$78.69	$78.70	$78.70
Purchase #7	$50.80	5.502%	$53.595	$53.60	$53.60	$53.60
7 purchase totals =	$647.25		$701.9726	$701.98	$702.00	$702.00