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	$69.48	3.441%	$71.8708	$71.87	$71.85	$71.90
Purchase #2	$103.60	13.287%	$117.3653	$117.37	$117.35	$117.40
Purchase #3	$38.64	13.304%	$43.7807	$43.78	$43.80	$43.80
Purchase #4	$26.94	3.147%	$27.7878	$27.79	$27.80	$27.80
Purchase #5	$58.85	7.857%	$63.4738	$63.47	$63.45	$63.50
Purchase #6	$33.61	5.774%	$35.5506	$35.55	$35.55	$35.60
Purchase #7	$62.48	6.713%	$66.6743	$66.67	$66.65	$66.70
7 purchase totals =	$393.60		$426.5033	$426.50	$426.45	$426.70