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	$158.66	9.675%	$174.0104	$174.01	$174.00	$174.00
Purchase #2	$198.92	11.730%	$222.2533	$222.25	$222.25	$222.30
Purchase #3	$96.46	7.291%	$103.4929	$103.49	$103.50	$103.50
Purchase #4	$56.58	11.663%	$63.1789	$63.18	$63.20	$63.20
Purchase #5	$80.74	8.732%	$87.7902	$87.79	$87.80	$87.80
Purchase #6	$63.75	13.439%	$72.3174	$72.32	$72.30	$72.30
Purchase #7	$40.27	13.285%	$45.6199	$45.62	$45.60	$45.60
7 purchase totals =	$695.38		$768.6630	$768.66	$768.65	$768.70