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	$241.74	10.631%	$267.4394	$267.44	$267.45	$267.40
Purchase #2	$33.87	6.233%	$35.9811	$35.98	$36.00	$36.00
Purchase #3	$66.37	13.516%	$75.3406	$75.34	$75.35	$75.30
Purchase #4	$64.77	12.535%	$72.8889	$72.89	$72.90	$72.90
Purchase #5	$59.93	9.566%	$65.6629	$65.66	$65.65	$65.70
Purchase #6	$15.78	11.251%	$17.5554	$17.56	$17.55	$17.60
Purchase #7	$236.37	7.712%	$254.5989	$254.60	$254.60	$254.60
7 purchase totals =	$718.83		$789.4672	$789.47	$789.50	$789.50