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	$105.30	8.155%	$113.8872	$113.89	$113.90	$113.90
Purchase #2	$238.78	12.484%	$268.5893	$268.59	$268.60	$268.60
Purchase #3	$104.89	9.172%	$114.5105	$114.51	$114.50	$114.50
Purchase #4	$194.70	6.861%	$208.0584	$208.06	$208.05	$208.10
Purchase #5	$40.48	4.275%	$42.2105	$42.21	$42.20	$42.20
Purchase #6	$189.85	3.429%	$196.36	$196.36	$196.35	$196.40
Purchase #7	$80.79	11.506%	$90.0857	$90.09	$90.10	$90.10
7 purchase totals =	$954.79		$1,033.7016	$1,033.71	$1,033.70	$1,033.80