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	$53.29	3.824%	$55.3278	$55.33	$55.35	$55.30
Purchase #2	$196.48	5.763%	$207.8031	$207.80	$207.80	$207.80
Purchase #3	$234.44	5.723%	$247.857	$247.86	$247.85	$247.90
Purchase #4	$164.86	9.508%	$180.5349	$180.53	$180.55	$180.50
Purchase #5	$111.51	6.799%	$119.0916	$119.09	$119.10	$119.10
Purchase #6	$40.70	3.277%	$42.0337	$42.03	$42.05	$42.00
Purchase #7	$99.77	12.145%	$111.8871	$111.89	$111.90	$111.90
7 purchase totals =	$901.05		$964.5352	$964.53	$964.60	$964.50