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	$14.50	7.157%	$15.5378	$15.54	$15.55	$15.50
Purchase #2	$12.35	6.799%	$13.1897	$13.19	$13.20	$13.20
Purchase #3	$180.52	12.635%	$203.3287	$203.33	$203.35	$203.30
Purchase #4	$132.62	8.236%	$143.5426	$143.54	$143.55	$143.50
Purchase #5	$9.49	10.813%	$10.5162	$10.52	$10.50	$10.50
Purchase #6	$89.63	10.615%	$99.1442	$99.14	$99.15	$99.10
Purchase #7	$116.51	10.622%	$128.8857	$128.89	$128.90	$128.90
7 purchase totals =	$555.62		$614.1449	$614.15	$614.20	$614.00