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	$62.63	8.367%	$67.8703	$67.87	$67.85	$67.90
Purchase #2	$11.96	3.507%	$12.3794	$12.38	$12.40	$12.40
Purchase #3	$107.36	6.680%	$114.5316	$114.53	$114.55	$114.50
Purchase #4	$245.50	12.372%	$275.8733	$275.87	$275.85	$275.90
Purchase #5	$61.82	7.665%	$66.5585	$66.56	$66.55	$66.60
Purchase #6	$90.77	4.169%	$94.5542	$94.55	$94.55	$94.60
Purchase #7	$186.32	7.410%	$200.1263	$200.13	$200.15	$200.10
7 purchase totals =	$766.36		$831.8936	$831.89	$831.90	$832.00