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	$36.66	10.815%	$40.6248	$40.62	$40.60	$40.60
Purchase #2	$162.59	11.715%	$181.6374	$181.64	$181.65	$181.60
Purchase #3	$226.35	7.184%	$242.611	$242.61	$242.60	$242.60
Purchase #4	$211.80	6.516%	$225.6009	$225.60	$225.60	$225.60
Purchase #5	$37.62	6.257%	$39.9739	$39.97	$39.95	$40.00
Purchase #6	$194.52	12.563%	$218.9575	$218.96	$218.95	$219.00
Purchase #7	$158.91	9.569%	$174.1161	$174.12	$174.10	$174.10
7 purchase totals =	$1,028.45		$1,123.5216	$1,123.52	$1,123.45	$1,123.50