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	$141.57	9.867%	$155.5387	$155.54	$155.55	$155.50
Purchase #2	$250.69	6.365%	$266.6464	$266.65	$266.65	$266.60
Purchase #3	$143.34	9.379%	$156.7839	$156.78	$156.80	$156.80
Purchase #4	$103.41	6.143%	$109.7625	$109.76	$109.75	$109.80
Purchase #5	$148.93	4.612%	$155.7987	$155.80	$155.80	$155.80
Purchase #6	$63.39	3.321%	$65.4952	$65.50	$65.50	$65.50
Purchase #7	$183.59	8.622%	$199.4191	$199.42	$199.40	$199.40
7 purchase totals =	$1,034.92		$1,109.4445	$1,109.45	$1,109.45	$1,109.40