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	$250.95	12.639%	$282.6676	$282.67	$282.65	$282.70
Purchase #2	$127.48	3.389%	$131.8003	$131.80	$131.80	$131.80
Purchase #3	$203.53	13.815%	$231.6477	$231.65	$231.65	$231.60
Purchase #4	$225.61	11.464%	$251.4739	$251.47	$251.45	$251.50
Purchase #5	$157.94	5.150%	$166.0739	$166.07	$166.05	$166.10
Purchase #6	$103.88	5.357%	$109.4449	$109.44	$109.45	$109.40
Purchase #7	$31.39	11.831%	$35.1038	$35.10	$35.10	$35.10
7 purchase totals =	$1,100.78		$1,208.2121	$1,208.20	$1,208.15	$1,208.20