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	$200.26	5.575%	$211.4245	$211.42	$211.40	$211.40
Purchase #2	$212.86	4.681%	$222.824	$222.82	$222.80	$222.80
Purchase #3	$31.62	7.169%	$33.8868	$33.89	$33.90	$33.90
Purchase #4	$215.83	11.707%	$241.0972	$241.10	$241.10	$241.10
Purchase #5	$210.50	8.310%	$227.9926	$227.99	$228.00	$228.00
Purchase #6	$226.52	8.321%	$245.3687	$245.37	$245.35	$245.40
Purchase #7	$51.66	8.186%	$55.8889	$55.89	$55.90	$55.90
7 purchase totals =	$1,149.25		$1,238.4827	$1,238.48	$1,238.45	$1,238.50