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	$223.65	7.256%	$239.878	$239.88	$239.90	$239.90
Purchase #2	$104.42	11.578%	$116.5097	$116.51	$116.50	$116.50
Purchase #3	$12.62	7.642%	$13.5844	$13.58	$13.60	$13.60
Purchase #4	$200.82	10.535%	$221.9764	$221.98	$222.00	$222.00
Purchase #5	$50.26	5.240%	$52.8936	$52.89	$52.90	$52.90
Purchase #6	$246.63	4.863%	$258.6236	$258.62	$258.60	$258.60
Purchase #7	$137.58	10.816%	$152.4607	$152.46	$152.45	$152.50
7 purchase totals =	$975.98		$1,055.9264	$1,055.92	$1,055.95	$1,056.00