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	$161.39	11.214%	$179.4883	$179.49	$179.50	$179.50
Purchase #2	$143.77	7.624%	$154.731	$154.73	$154.75	$154.70
Purchase #3	$140.73	12.691%	$158.59	$158.59	$158.60	$158.60
Purchase #4	$174.48	10.498%	$192.7969	$192.80	$192.80	$192.80
Purchase #5	$50.35	11.403%	$56.0914	$56.09	$56.10	$56.10
Purchase #6	$206.59	7.563%	$222.2144	$222.21	$222.20	$222.20
Purchase #7	$122.35	11.659%	$136.6148	$136.61	$136.60	$136.60
7 purchase totals =	$999.66		$1,100.5268	$1,100.52	$1,100.55	$1,100.50