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	$180.26	10.601%	$199.3694	$199.37	$199.35	$199.40
Purchase #2	$124.96	13.305%	$141.5859	$141.59	$141.60	$141.60
Purchase #3	$215.75	11.607%	$240.7921	$240.79	$240.80	$240.80
Purchase #4	$96.32	7.577%	$103.6182	$103.62	$103.60	$103.60
Purchase #5	$36.96	8.631%	$40.15	$40.15	$40.15	$40.20
Purchase #6	$176.72	13.678%	$200.8918	$200.89	$200.90	$200.90
Purchase #7	$109.32	12.348%	$122.8188	$122.82	$122.80	$122.80
7 purchase totals =	$940.29		$1,049.2262	$1,049.23	$1,049.20	$1,049.30