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	$148.78	7.416%	$159.8135	$159.81	$159.80	$159.80
Purchase #2	$161.38	8.203%	$174.618	$174.62	$174.60	$174.60
Purchase #3	$231.68	12.116%	$259.7503	$259.75	$259.75	$259.80
Purchase #4	$33.29	7.534%	$35.7981	$35.80	$35.80	$35.80
Purchase #5	$49.25	13.352%	$55.8259	$55.83	$55.85	$55.80
Purchase #6	$63.67	13.766%	$72.4348	$72.43	$72.45	$72.40
Purchase #7	$123.54	11.382%	$137.6013	$137.60	$137.60	$137.60
7 purchase totals =	$811.59		$895.8419	$895.84	$895.85	$895.80