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	$200.25	3.324%	$206.9063	$206.91	$206.90	$206.90
Purchase #2	$166.46	7.302%	$178.6149	$178.61	$178.60	$178.60
Purchase #3	$58.28	5.495%	$61.4825	$61.48	$61.50	$61.50
Purchase #4	$85.53	5.792%	$90.4839	$90.48	$90.50	$90.50
Purchase #5	$111.85	3.385%	$115.6361	$115.64	$115.65	$115.60
Purchase #6	$215.80	5.524%	$227.7208	$227.72	$227.70	$227.70
Purchase #7	$93.47	13.205%	$105.8127	$105.81	$105.80	$105.80
7 purchase totals =	$931.64		$986.6572	$986.65	$986.65	$986.60