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	$176.42	11.269%	$196.3008	$196.30	$196.30	$196.30
Purchase #2	$212.67	13.241%	$240.8296	$240.83	$240.85	$240.80
Purchase #3	$121.86	13.125%	$137.8541	$137.85	$137.85	$137.90
Purchase #4	$108.41	4.730%	$113.5378	$113.54	$113.55	$113.50
Purchase #5	$73.31	12.161%	$82.2252	$82.23	$82.25	$82.20
Purchase #6	$171.25	10.558%	$189.3306	$189.33	$189.35	$189.30
Purchase #7	$100.95	4.849%	$105.8451	$105.85	$105.85	$105.80
7 purchase totals =	$964.87		$1,065.9232	$1,065.93	$1,066.00	$1,065.80