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	$127.27	5.127%	$133.7951	$133.80	$133.80	$133.80
Purchase #2	$158.77	10.761%	$175.8552	$175.86	$175.85	$175.90
Purchase #3	$232.69	3.179%	$240.0872	$240.09	$240.10	$240.10
Purchase #4	$53.80	10.687%	$59.5496	$59.55	$59.55	$59.50
Purchase #5	$76.98	13.754%	$87.5678	$87.57	$87.55	$87.60
Purchase #6	$169.29	13.719%	$192.5149	$192.51	$192.50	$192.50
Purchase #7	$145.31	10.332%	$160.3234	$160.32	$160.30	$160.30
7 purchase totals =	$964.11		$1,049.6932	$1,049.70	$1,049.65	$1,049.70