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	$239.49	8.260%	$259.2719	$259.27	$259.25	$259.30
Purchase #2	$224.86	11.429%	$250.5592	$250.56	$250.55	$250.60
Purchase #3	$172.81	3.201%	$178.3416	$178.34	$178.35	$178.30
Purchase #4	$83.91	4.272%	$87.4946	$87.49	$87.50	$87.50
Purchase #5	$77.83	6.732%	$83.0695	$83.07	$83.05	$83.10
Purchase #6	$165.35	10.446%	$182.6225	$182.62	$182.60	$182.60
Purchase #7	$98.99	6.582%	$105.5055	$105.51	$105.50	$105.50
7 purchase totals =	$1,063.24		$1,146.8648	$1,146.86	$1,146.80	$1,146.90