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	$205.53	5.312%	$216.4478	$216.45	$216.45	$216.40
Purchase #2	$128.67	8.709%	$139.8759	$139.88	$139.90	$139.90
Purchase #3	$162.95	6.421%	$173.413	$173.41	$173.40	$173.40
Purchase #4	$162.32	9.845%	$178.3004	$178.30	$178.30	$178.30
Purchase #5	$13.85	5.498%	$14.6115	$14.61	$14.60	$14.60
Purchase #6	$200.76	3.637%	$208.0616	$208.06	$208.05	$208.10
Purchase #7	$139.37	9.737%	$152.9405	$152.94	$152.95	$152.90
7 purchase totals =	$1,013.45		$1,083.6507	$1,083.65	$1,083.65	$1,083.60