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	$100.32	10.728%	$111.0823	$111.08	$111.10	$111.10
Purchase #2	$185.47	13.277%	$210.0949	$210.09	$210.10	$210.10
Purchase #3	$178.93	5.265%	$188.3507	$188.35	$188.35	$188.40
Purchase #4	$84.85	10.127%	$93.4428	$93.44	$93.45	$93.40
Purchase #5	$137.93	4.676%	$144.3796	$144.38	$144.40	$144.40
Purchase #6	$100.26	7.231%	$107.5098	$107.51	$107.50	$107.50
Purchase #7	$224.90	13.405%	$255.0478	$255.05	$255.05	$255.00
7 purchase totals =	$1,012.66		$1,109.9079	$1,109.90	$1,109.95	$1,109.90