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	$208.37	6.665%	$222.2579	$222.26	$222.25	$222.30
Purchase #2	$123.51	12.828%	$139.3539	$139.35	$139.35	$139.40
Purchase #3	$32.96	8.378%	$35.7214	$35.72	$35.70	$35.70
Purchase #4	$228.72	3.866%	$237.5623	$237.56	$237.55	$237.60
Purchase #5	$212.98	13.438%	$241.6003	$241.60	$241.60	$241.60
Purchase #6	$112.76	11.337%	$125.5436	$125.54	$125.55	$125.50
Purchase #7	$43.53	8.498%	$47.2292	$47.23	$47.25	$47.20
7 purchase totals =	$962.83		$1,049.2686	$1,049.26	$1,049.25	$1,049.30