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	$94.75	9.459%	$103.7124	$103.71	$103.70	$103.70
Purchase #2	$223.89	4.679%	$234.3658	$234.37	$234.35	$234.40
Purchase #3	$196.25	9.822%	$215.5257	$215.53	$215.55	$215.50
Purchase #4	$26.57	7.117%	$28.461	$28.46	$28.45	$28.50
Purchase #5	$125.82	11.269%	$139.9987	$140.00	$140.00	$140.00
Purchase #6	$84.55	7.550%	$90.9335	$90.93	$90.95	$90.90
Purchase #7	$213.93	8.215%	$231.5043	$231.50	$231.50	$231.50
7 purchase totals =	$965.76		$1,044.5014	$1,044.50	$1,044.50	$1,044.50