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	$9.98	12.799%	$11.2573	$11.26	$11.25	$11.30
Purchase #2	$116.90	9.798%	$128.3539	$128.35	$128.35	$128.40
Purchase #3	$101.90	9.344%	$111.4215	$111.42	$111.40	$111.40
Purchase #4	$236.37	5.394%	$249.1198	$249.12	$249.10	$249.10
Purchase #5	$124.71	5.389%	$131.4306	$131.43	$131.45	$131.40
Purchase #6	$240.81	13.397%	$273.0713	$273.07	$273.05	$273.10
Purchase #7	$144.29	7.392%	$154.9559	$154.96	$154.95	$155.00
7 purchase totals =	$974.96		$1,059.6103	$1,059.61	$1,059.55	$1,059.70