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	$126.78	8.454%	$137.498	$137.50	$137.50	$137.50
Purchase #2	$153.62	11.699%	$171.592	$171.59	$171.60	$171.60
Purchase #3	$164.68	11.529%	$183.666	$183.67	$183.65	$183.70
Purchase #4	$119.47	3.230%	$123.3289	$123.33	$123.35	$123.30
Purchase #5	$198.67	4.782%	$208.1704	$208.17	$208.15	$208.20
Purchase #6	$180.92	8.797%	$196.8355	$196.84	$196.85	$196.80
Purchase #7	$189.49	13.179%	$214.4629	$214.46	$214.45	$214.50
7 purchase totals =	$1,133.63		$1,235.5537	$1,235.56	$1,235.55	$1,235.60