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	$111.78	10.189%	$123.1693	$123.17	$123.15	$123.20
Purchase #2	$173.56	7.265%	$186.1691	$186.17	$186.15	$186.20
Purchase #3	$223.33	11.806%	$249.6963	$249.70	$249.70	$249.70
Purchase #4	$143.93	10.387%	$158.88	$158.88	$158.90	$158.90
Purchase #5	$50.43	10.336%	$55.6424	$55.64	$55.65	$55.60
Purchase #6	$211.52	4.545%	$221.1336	$221.13	$221.15	$221.10
Purchase #7	$76.86	6.270%	$81.6791	$81.68	$81.70	$81.70
7 purchase totals =	$991.41		$1,076.3698	$1,076.37	$1,076.40	$1,076.40