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	$136.48	10.198%	$150.3982	$150.40	$150.40	$150.40
Purchase #2	$18.58	11.710%	$20.7557	$20.76	$20.75	$20.80
Purchase #3	$164.82	8.869%	$179.4379	$179.44	$179.45	$179.40
Purchase #4	$115.52	3.448%	$119.5031	$119.50	$119.50	$119.50
Purchase #5	$246.52	6.126%	$261.6218	$261.62	$261.60	$261.60
Purchase #6	$238.98	11.227%	$265.8103	$265.81	$265.80	$265.80
Purchase #7	$94.49	6.152%	$100.303	$100.30	$100.30	$100.30
7 purchase totals =	$1,015.39		$1,097.8300	$1,097.83	$1,097.80	$1,097.80