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	$52.94	12.136%	$59.3648	$59.36	$59.35	$59.40
Purchase #2	$206.79	4.681%	$216.4698	$216.47	$216.45	$216.50
Purchase #3	$246.98	9.472%	$270.3739	$270.37	$270.35	$270.40
Purchase #4	$116.30	5.682%	$122.9082	$122.91	$122.90	$122.90
Purchase #5	$42.92	9.269%	$46.8983	$46.90	$46.90	$46.90
Purchase #6	$7.34	7.671%	$7.9031	$7.90	$7.90	$7.90
Purchase #7	$28.45	11.599%	$31.7499	$31.75	$31.75	$31.70
7 purchase totals =	$701.72		$755.6680	$755.66	$755.60	$755.70