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	$87.90	5.648%	$92.8646	$92.86	$92.85	$92.90
Purchase #2	$102.64	6.790%	$109.6093	$109.61	$109.60	$109.60
Purchase #3	$200.95	10.863%	$222.7792	$222.78	$222.80	$222.80
Purchase #4	$85.63	10.128%	$94.3026	$94.30	$94.30	$94.30
Purchase #5	$94.92	5.192%	$99.8482	$99.85	$99.85	$99.80
Purchase #6	$112.47	4.743%	$117.8045	$117.80	$117.80	$117.80
Purchase #7	$67.90	11.348%	$75.6053	$75.61	$75.60	$75.60
7 purchase totals =	$752.41		$812.8137	$812.81	$812.80	$812.80