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	$119.31	10.218%	$131.5011	$131.50	$131.50	$131.50
Purchase #2	$203.40	4.529%	$212.612	$212.61	$212.60	$212.60
Purchase #3	$30.72	3.663%	$31.8453	$31.85	$31.85	$31.80
Purchase #4	$133.70	4.266%	$139.4036	$139.40	$139.40	$139.40
Purchase #5	$228.86	11.731%	$255.7076	$255.71	$255.70	$255.70
Purchase #6	$36.31	9.868%	$39.8931	$39.89	$39.90	$39.90
Purchase #7	$200.57	6.396%	$213.3985	$213.40	$213.40	$213.40
7 purchase totals =	$952.87		$1,024.3612	$1,024.36	$1,024.35	$1,024.30