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	$126.75	10.832%	$140.4796	$140.48	$140.50	$140.50
Purchase #2	$113.38	13.200%	$128.3462	$128.35	$128.35	$128.30
Purchase #3	$176.29	13.657%	$200.3659	$200.37	$200.35	$200.40
Purchase #4	$146.71	6.106%	$155.6681	$155.67	$155.65	$155.70
Purchase #5	$156.85	3.626%	$162.5374	$162.54	$162.55	$162.50
Purchase #6	$68.71	7.180%	$73.6434	$73.64	$73.65	$73.60
Purchase #7	$163.96	3.349%	$169.451	$169.45	$169.45	$169.50
7 purchase totals =	$952.65		$1,030.4916	$1,030.50	$1,030.50	$1,030.50