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	$198.34	5.605%	$209.457	$209.46	$209.45	$209.50
Purchase #2	$23.98	11.726%	$26.7919	$26.79	$26.80	$26.80
Purchase #3	$103.34	8.258%	$111.8738	$111.87	$111.85	$111.90
Purchase #4	$244.60	6.204%	$259.775	$259.78	$259.80	$259.80
Purchase #5	$41.42	5.730%	$43.7934	$43.79	$43.80	$43.80
Purchase #6	$105.56	7.396%	$113.3672	$113.37	$113.35	$113.40
Purchase #7	$125.66	4.508%	$131.3248	$131.32	$131.30	$131.30
7 purchase totals =	$842.90		$896.3831	$896.38	$896.35	$896.50