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	$171.27	12.584%	$192.8226	$192.82	$192.80	$192.80
Purchase #2	$76.52	7.643%	$82.3684	$82.37	$82.35	$82.40
Purchase #3	$211.95	7.249%	$227.3143	$227.31	$227.30	$227.30
Purchase #4	$43.82	4.223%	$45.6705	$45.67	$45.65	$45.70
Purchase #5	$246.26	6.218%	$261.5724	$261.57	$261.55	$261.60
Purchase #6	$83.64	6.455%	$89.039	$89.04	$89.05	$89.00
Purchase #7	$161.95	5.622%	$171.0548	$171.05	$171.05	$171.10
7 purchase totals =	$995.41		$1,069.8420	$1,069.83	$1,069.75	$1,069.90