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	$112.78	9.866%	$123.9069	$123.91	$123.90	$123.90
Purchase #2	$174.71	12.464%	$196.4859	$196.49	$196.50	$196.50
Purchase #3	$174.88	8.573%	$189.8725	$189.87	$189.85	$189.90
Purchase #4	$248.30	13.784%	$282.5257	$282.53	$282.55	$282.50
Purchase #5	$137.83	13.625%	$156.6093	$156.61	$156.60	$156.60
Purchase #6	$212.69	5.382%	$224.137	$224.14	$224.15	$224.10
Purchase #7	$31.86	3.381%	$32.9372	$32.94	$32.95	$32.90
7 purchase totals =	$1,093.05		$1,206.4745	$1,206.49	$1,206.50	$1,206.40