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	$128.74	12.191%	$144.4347	$144.43	$144.45	$144.40
Purchase #2	$111.74	5.542%	$117.9326	$117.93	$117.95	$117.90
Purchase #3	$162.90	10.188%	$179.4963	$179.50	$179.50	$179.50
Purchase #4	$194.61	7.166%	$208.5558	$208.56	$208.55	$208.60
Purchase #5	$119.89	3.303%	$123.85	$123.85	$123.85	$123.90
Purchase #6	$10.96	5.230%	$11.5332	$11.53	$11.55	$11.50
Purchase #7	$148.92	10.545%	$164.6236	$164.62	$164.60	$164.60
7 purchase totals =	$877.76		$950.4262	$950.42	$950.45	$950.40