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	$116.47	6.107%	$123.5828	$123.58	$123.60	$123.60
Purchase #2	$6.63	10.521%	$7.3275	$7.33	$7.35	$7.30
Purchase #3	$143.46	12.696%	$161.6737	$161.67	$161.65	$161.70
Purchase #4	$177.47	5.677%	$187.545	$187.55	$187.55	$187.50
Purchase #5	$169.76	8.634%	$184.4171	$184.42	$184.40	$184.40
Purchase #6	$120.66	6.458%	$128.4522	$128.45	$128.45	$128.50
Purchase #7	$72.90	13.597%	$82.8122	$82.81	$82.80	$82.80
7 purchase totals =	$807.35		$875.8105	$875.81	$875.80	$875.80