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	$101.33	11.235%	$112.7144	$112.71	$112.70	$112.70
Purchase #2	$126.59	10.179%	$139.4756	$139.48	$139.50	$139.50
Purchase #3	$159.43	7.832%	$171.9166	$171.92	$171.90	$171.90
Purchase #4	$43.33	12.365%	$48.6878	$48.69	$48.70	$48.70
Purchase #5	$203.93	6.217%	$216.6083	$216.61	$216.60	$216.60
Purchase #6	$9.64	12.670%	$10.8614	$10.86	$10.85	$10.90
Purchase #7	$153.87	8.695%	$167.249	$167.25	$167.25	$167.20
7 purchase totals =	$798.12		$867.5131	$867.52	$867.50	$867.50