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	$208.89	3.790%	$216.8069	$216.81	$216.80	$216.80
Purchase #2	$115.95	11.727%	$129.5475	$129.55	$129.55	$129.50
Purchase #3	$153.68	6.708%	$163.9889	$163.99	$164.00	$164.00
Purchase #4	$134.89	3.678%	$139.8513	$139.85	$139.85	$139.90
Purchase #5	$141.25	10.746%	$156.4287	$156.43	$156.45	$156.40
Purchase #6	$153.55	3.279%	$158.5849	$158.58	$158.60	$158.60
Purchase #7	$172.58	7.741%	$185.9394	$185.94	$185.95	$185.90
7 purchase totals =	$1,080.79		$1,151.1476	$1,151.15	$1,151.20	$1,151.10