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	$117.86	6.516%	$125.5398	$125.54	$125.55	$125.50
Purchase #2	$169.95	9.158%	$185.514	$185.51	$185.50	$185.50
Purchase #3	$206.77	13.405%	$234.4875	$234.49	$234.50	$234.50
Purchase #4	$87.92	10.651%	$97.2844	$97.28	$97.30	$97.30
Purchase #5	$123.45	13.325%	$139.8997	$139.90	$139.90	$139.90
Purchase #6	$131.26	9.758%	$144.0684	$144.07	$144.05	$144.10
Purchase #7	$148.97	7.491%	$160.1293	$160.13	$160.15	$160.10
7 purchase totals =	$986.18		$1,086.9231	$1,086.92	$1,086.95	$1,086.90