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	$241.57	4.551%	$252.5639	$252.56	$252.55	$252.60
Purchase #2	$89.77	11.509%	$100.1016	$100.10	$100.10	$100.10
Purchase #3	$213.44	4.307%	$222.6329	$222.63	$222.65	$222.60
Purchase #4	$22.80	7.358%	$24.4776	$24.48	$24.50	$24.50
Purchase #5	$62.76	3.770%	$65.1261	$65.13	$65.15	$65.10
Purchase #6	$186.36	12.406%	$209.4798	$209.48	$209.50	$209.50
Purchase #7	$42.88	11.784%	$47.933	$47.93	$47.95	$47.90
7 purchase totals =	$859.58		$922.3149	$922.31	$922.40	$922.30