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	$101.77	10.494%	$112.4497	$112.45	$112.45	$112.40
Purchase #2	$175.61	11.493%	$195.7929	$195.79	$195.80	$195.80
Purchase #3	$231.46	11.410%	$257.8696	$257.87	$257.85	$257.90
Purchase #4	$110.92	11.382%	$123.5449	$123.54	$123.55	$123.50
Purchase #5	$121.32	8.457%	$131.58	$131.58	$131.60	$131.60
Purchase #6	$128.86	5.602%	$136.0787	$136.08	$136.10	$136.10
Purchase #7	$56.96	5.386%	$60.0279	$60.03	$60.05	$60.00
7 purchase totals =	$926.90		$1,017.3437	$1,017.34	$1,017.40	$1,017.30