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	$75.79	10.317%	$83.6093	$83.61	$83.60	$83.60
Purchase #2	$184.77	10.196%	$203.6091	$203.61	$203.60	$203.60
Purchase #3	$250.99	13.277%	$284.3139	$284.31	$284.30	$284.30
Purchase #4	$192.84	3.595%	$199.7726	$199.77	$199.75	$199.80
Purchase #5	$34.29	8.558%	$37.2245	$37.22	$37.20	$37.20
Purchase #6	$54.87	9.105%	$59.8659	$59.87	$59.85	$59.90
Purchase #7	$146.86	8.353%	$159.1272	$159.13	$159.15	$159.10
7 purchase totals =	$940.41		$1,027.5225	$1,027.52	$1,027.45	$1,027.50