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	$40.25	9.762%	$44.1792	$44.18	$44.20	$44.20
Purchase #2	$203.61	10.584%	$225.1601	$225.16	$225.15	$225.20
Purchase #3	$73.86	5.771%	$78.1225	$78.12	$78.10	$78.10
Purchase #4	$239.35	9.847%	$262.9188	$262.92	$262.90	$262.90
Purchase #5	$219.85	9.863%	$241.5338	$241.53	$241.55	$241.50
Purchase #6	$197.38	11.769%	$220.6097	$220.61	$220.60	$220.60
Purchase #7	$240.93	13.466%	$273.3736	$273.37	$273.35	$273.40
7 purchase totals =	$1,215.23		$1,345.8977	$1,345.89	$1,345.85	$1,345.90