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	$42.78	12.438%	$48.101	$48.10	$48.10	$48.10
Purchase #2	$118.54	4.333%	$123.6763	$123.68	$123.70	$123.70
Purchase #3	$59.78	13.500%	$67.8503	$67.85	$67.85	$67.90
Purchase #4	$137.59	7.599%	$148.0455	$148.05	$148.05	$148.00
Purchase #5	$196.60	11.567%	$219.3407	$219.34	$219.35	$219.30
Purchase #6	$165.45	6.770%	$176.651	$176.65	$176.65	$176.70
Purchase #7	$226.39	13.171%	$256.2078	$256.21	$256.20	$256.20
7 purchase totals =	$947.13		$1,039.8726	$1,039.88	$1,039.90	$1,039.90