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	$131.44	9.341%	$143.7178	$143.72	$143.70	$143.70
Purchase #2	$139.41	6.172%	$148.0144	$148.01	$148.00	$148.00
Purchase #3	$212.71	4.564%	$222.4181	$222.42	$222.40	$222.40
Purchase #4	$126.78	3.511%	$131.2312	$131.23	$131.25	$131.20
Purchase #5	$219.96	7.736%	$236.9761	$236.98	$237.00	$237.00
Purchase #6	$172.36	8.748%	$187.4381	$187.44	$187.45	$187.40
Purchase #7	$34.69	7.612%	$37.3306	$37.33	$37.35	$37.30
7 purchase totals =	$1,037.35		$1,107.1263	$1,107.13	$1,107.15	$1,107.00