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	$12.69	8.232%	$13.7346	$13.73	$13.75	$13.70
Purchase #2	$61.75	7.420%	$66.3319	$66.33	$66.35	$66.30
Purchase #3	$35.76	12.444%	$40.21	$40.21	$40.20	$40.20
Purchase #4	$196.64	8.243%	$212.849	$212.85	$212.85	$212.80
Purchase #5	$127.32	13.497%	$144.5044	$144.50	$144.50	$144.50
Purchase #6	$118.78	6.285%	$126.2453	$126.25	$126.25	$126.20
Purchase #7	$112.41	6.278%	$119.4671	$119.47	$119.45	$119.50
7 purchase totals =	$665.35		$723.3423	$723.34	$723.35	$723.20