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	$121.50	8.599%	$131.9478	$131.95	$131.95	$131.90
Purchase #2	$42.35	9.577%	$46.4059	$46.41	$46.40	$46.40
Purchase #3	$62.79	4.306%	$65.4937	$65.49	$65.50	$65.50
Purchase #4	$18.77	5.451%	$19.7932	$19.79	$19.80	$19.80
Purchase #5	$54.63	13.258%	$61.8728	$61.87	$61.85	$61.90
Purchase #6	$126.81	4.265%	$132.2184	$132.22	$132.20	$132.20
Purchase #7	$76.56	13.474%	$86.8757	$86.88	$86.90	$86.90
7 purchase totals =	$503.41		$544.6075	$544.61	$544.60	$544.60