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	$213.98	12.380%	$240.4707	$240.47	$240.45	$240.50
Purchase #2	$190.50	3.243%	$196.6779	$196.68	$196.70	$196.70
Purchase #3	$103.69	13.481%	$117.6684	$117.67	$117.65	$117.70
Purchase #4	$211.73	13.159%	$239.5916	$239.59	$239.60	$239.60
Purchase #5	$127.39	12.687%	$143.552	$143.55	$143.55	$143.60
Purchase #6	$14.48	13.826%	$16.482	$16.48	$16.50	$16.50
Purchase #7	$90.89	6.478%	$96.7779	$96.78	$96.80	$96.80
7 purchase totals =	$952.66		$1,051.2205	$1,051.22	$1,051.25	$1,051.40