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	$50.51	7.328%	$54.2114	$54.21	$54.20	$54.20
Purchase #2	$211.47	10.115%	$232.8602	$232.86	$232.85	$232.90
Purchase #3	$44.33	9.252%	$48.4314	$48.43	$48.45	$48.40
Purchase #4	$163.48	10.419%	$180.513	$180.51	$180.50	$180.50
Purchase #5	$184.33	3.330%	$190.4682	$190.47	$190.45	$190.50
Purchase #6	$143.69	7.345%	$154.244	$154.24	$154.25	$154.20
Purchase #7	$140.81	10.468%	$155.55	$155.55	$155.55	$155.60
7 purchase totals =	$938.62		$1,016.2782	$1,016.27	$1,016.25	$1,016.30