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	$188.46	6.397%	$200.5158	$200.52	$200.50	$200.50
Purchase #2	$161.61	9.143%	$176.386	$176.39	$176.40	$176.40
Purchase #3	$161.30	7.190%	$172.8975	$172.90	$172.90	$172.90
Purchase #4	$62.83	7.360%	$67.4543	$67.45	$67.45	$67.50
Purchase #5	$213.35	10.638%	$236.0462	$236.05	$236.05	$236.00
Purchase #6	$138.82	12.280%	$155.8671	$155.87	$155.85	$155.90
Purchase #7	$165.91	4.557%	$173.4705	$173.47	$173.45	$173.50
7 purchase totals =	$1,092.28		$1,182.6374	$1,182.65	$1,182.60	$1,182.70