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	$174.56	9.160%	$190.5497	$190.55	$190.55	$190.50
Purchase #2	$67.65	13.328%	$76.6664	$76.67	$76.65	$76.70
Purchase #3	$6.85	7.115%	$7.3374	$7.34	$7.35	$7.30
Purchase #4	$120.90	6.300%	$128.5167	$128.52	$128.50	$128.50
Purchase #5	$200.35	8.741%	$217.8626	$217.86	$217.85	$217.90
Purchase #6	$43.52	13.296%	$49.3064	$49.31	$49.30	$49.30
Purchase #7	$232.57	7.308%	$249.5662	$249.57	$249.55	$249.60
7 purchase totals =	$846.40		$919.8054	$919.82	$919.75	$919.80