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	$128.39	11.371%	$142.9892	$142.99	$143.00	$143.00
Purchase #2	$11.84	12.637%	$13.3362	$13.34	$13.35	$13.30
Purchase #3	$98.62	13.396%	$111.8311	$111.83	$111.85	$111.80
Purchase #4	$169.76	9.740%	$186.2946	$186.29	$186.30	$186.30
Purchase #5	$78.34	13.506%	$88.9206	$88.92	$88.90	$88.90
Purchase #6	$239.71	9.517%	$262.5232	$262.52	$262.50	$262.50
Purchase #7	$127.80	5.538%	$134.8776	$134.88	$134.90	$134.90
7 purchase totals =	$854.46		$940.7725	$940.77	$940.80	$940.70