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	$56.76	9.773%	$62.3072	$62.31	$62.30	$62.30
Purchase #2	$204.26	10.244%	$225.1844	$225.18	$225.20	$225.20
Purchase #3	$61.93	5.352%	$65.2445	$65.24	$65.25	$65.20
Purchase #4	$241.44	6.810%	$257.8821	$257.88	$257.90	$257.90
Purchase #5	$86.52	10.719%	$95.7941	$95.79	$95.80	$95.80
Purchase #6	$123.33	6.716%	$131.6128	$131.61	$131.60	$131.60
Purchase #7	$28.44	10.542%	$31.4381	$31.44	$31.45	$31.40
7 purchase totals =	$802.68		$869.4632	$869.45	$869.50	$869.40