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	$125.69	5.128%	$132.1354	$132.14	$132.15	$132.10
Purchase #2	$40.51	12.696%	$45.6531	$45.65	$45.65	$45.70
Purchase #3	$221.52	7.504%	$238.1429	$238.14	$238.15	$238.10
Purchase #4	$235.91	9.522%	$258.3734	$258.37	$258.35	$258.40
Purchase #5	$102.48	9.456%	$112.1705	$112.17	$112.15	$112.20
Purchase #6	$189.78	13.267%	$214.9581	$214.96	$214.95	$215.00
Purchase #7	$85.44	11.294%	$95.0896	$95.09	$95.10	$95.10
7 purchase totals =	$1,001.33		$1,096.5230	$1,096.52	$1,096.50	$1,096.60