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	$107.37	10.867%	$119.0379	$119.04	$119.05	$119.00
Purchase #2	$80.26	4.463%	$83.842	$83.84	$83.85	$83.80
Purchase #3	$225.80	10.588%	$249.7077	$249.71	$249.70	$249.70
Purchase #4	$126.89	3.545%	$131.3883	$131.39	$131.40	$131.40
Purchase #5	$150.80	3.342%	$155.8397	$155.84	$155.85	$155.80
Purchase #6	$125.35	7.323%	$134.5294	$134.53	$134.55	$134.50
Purchase #7	$89.31	12.272%	$100.2701	$100.27	$100.25	$100.30
7 purchase totals =	$905.78		$974.6151	$974.62	$974.65	$974.50