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	$40.94	10.780%	$45.3533	$45.35	$45.35	$45.40
Purchase #2	$212.48	4.136%	$221.2682	$221.27	$221.25	$221.30
Purchase #3	$229.77	10.503%	$253.9027	$253.90	$253.90	$253.90
Purchase #4	$176.50	13.618%	$200.5358	$200.54	$200.55	$200.50
Purchase #5	$10.95	13.492%	$12.4274	$12.43	$12.45	$12.40
Purchase #6	$51.60	5.514%	$54.4452	$54.45	$54.45	$54.40
Purchase #7	$173.82	7.371%	$186.6323	$186.63	$186.65	$186.60
7 purchase totals =	$896.06		$974.5649	$974.57	$974.60	$974.50