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	$199.78	11.382%	$222.519	$222.52	$222.50	$222.50
Purchase #2	$208.67	11.836%	$233.3682	$233.37	$233.35	$233.40
Purchase #3	$57.81	3.216%	$59.6692	$59.67	$59.65	$59.70
Purchase #4	$80.86	7.824%	$87.1865	$87.19	$87.20	$87.20
Purchase #5	$214.36	6.619%	$228.5485	$228.55	$228.55	$228.50
Purchase #6	$161.35	6.363%	$171.6167	$171.62	$171.60	$171.60
Purchase #7	$43.37	3.371%	$44.832	$44.83	$44.85	$44.80
7 purchase totals =	$966.20		$1,047.7401	$1,047.75	$1,047.70	$1,047.70