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	$134.95	3.646%	$139.8703	$139.87	$139.85	$139.90
Purchase #2	$32.31	10.127%	$35.582	$35.58	$35.60	$35.60
Purchase #3	$85.45	7.788%	$92.1048	$92.10	$92.10	$92.10
Purchase #4	$23.60	11.530%	$26.3211	$26.32	$26.30	$26.30
Purchase #5	$29.83	10.858%	$33.0689	$33.07	$33.05	$33.10
Purchase #6	$214.80	5.165%	$225.8944	$225.89	$225.90	$225.90
Purchase #7	$139.83	12.650%	$157.5185	$157.52	$157.50	$157.50
7 purchase totals =	$660.77		$710.3600	$710.35	$710.30	$710.40