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	$143.97	4.404%	$150.3104	$150.31	$150.30	$150.30
Purchase #2	$76.37	7.577%	$82.1566	$82.16	$82.15	$82.20
Purchase #3	$216.77	6.673%	$231.2351	$231.24	$231.25	$231.20
Purchase #4	$85.86	5.838%	$90.8725	$90.87	$90.85	$90.90
Purchase #5	$36.62	8.148%	$39.6038	$39.60	$39.60	$39.60
Purchase #6	$121.65	13.778%	$138.4109	$138.41	$138.40	$138.40
Purchase #7	$38.41	13.256%	$43.5016	$43.50	$43.50	$43.50
7 purchase totals =	$719.65		$776.0909	$776.09	$776.05	$776.10