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	$139.46	9.738%	$153.0406	$153.04	$153.05	$153.00
Purchase #2	$91.27	8.263%	$98.8116	$98.81	$98.80	$98.80
Purchase #3	$31.86	10.677%	$35.2617	$35.26	$35.25	$35.30
Purchase #4	$129.73	10.117%	$142.8548	$142.85	$142.85	$142.90
Purchase #5	$47.31	12.569%	$53.2564	$53.26	$53.25	$53.30
Purchase #6	$102.89	12.771%	$116.0301	$116.03	$116.05	$116.00
Purchase #7	$25.98	13.670%	$29.5315	$29.53	$29.55	$29.50
7 purchase totals =	$568.50		$628.7867	$628.78	$628.80	$628.80