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	$157.70	11.628%	$176.0374	$176.04	$176.05	$176.00
Purchase #2	$151.85	8.219%	$164.3306	$164.33	$164.35	$164.30
Purchase #3	$94.89	5.849%	$100.4401	$100.44	$100.45	$100.40
Purchase #4	$103.85	13.807%	$118.1886	$118.19	$118.20	$118.20
Purchase #5	$117.84	11.591%	$131.4988	$131.50	$131.50	$131.50
Purchase #6	$96.79	3.708%	$100.379	$100.38	$100.40	$100.40
Purchase #7	$200.81	8.767%	$218.415	$218.42	$218.40	$218.40
7 purchase totals =	$923.73		$1,009.2895	$1,009.30	$1,009.35	$1,009.20