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	$78.57	11.455%	$87.5702	$87.57	$87.55	$87.60
Purchase #2	$226.54	10.864%	$251.1513	$251.15	$251.15	$251.20
Purchase #3	$63.70	10.704%	$70.5184	$70.52	$70.50	$70.50
Purchase #4	$70.58	11.673%	$78.8188	$78.82	$78.80	$78.80
Purchase #5	$250.61	9.175%	$273.6035	$273.60	$273.60	$273.60
Purchase #6	$189.30	11.318%	$210.725	$210.73	$210.75	$210.70
Purchase #7	$137.35	9.705%	$150.6798	$150.68	$150.70	$150.70
7 purchase totals =	$1,016.65		$1,123.0670	$1,123.07	$1,123.05	$1,123.10