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	$81.76	4.834%	$85.7123	$85.71	$85.70	$85.70
Purchase #2	$206.86	5.757%	$218.7689	$218.77	$218.75	$218.80
Purchase #3	$84.68	9.660%	$92.8601	$92.86	$92.85	$92.90
Purchase #4	$177.88	10.402%	$196.3831	$196.38	$196.40	$196.40
Purchase #5	$52.65	4.252%	$54.8887	$54.89	$54.90	$54.90
Purchase #6	$140.31	7.326%	$150.5891	$150.59	$150.60	$150.60
Purchase #7	$161.93	9.120%	$176.698	$176.70	$176.70	$176.70
7 purchase totals =	$906.07		$975.9002	$975.90	$975.90	$976.00