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	$119.82	5.552%	$126.4724	$126.47	$126.45	$126.50
Purchase #2	$241.55	3.202%	$249.2844	$249.28	$249.30	$249.30
Purchase #3	$214.43	3.289%	$221.4826	$221.48	$221.50	$221.50
Purchase #4	$95.55	6.591%	$101.8477	$101.85	$101.85	$101.80
Purchase #5	$56.66	4.246%	$59.0658	$59.07	$59.05	$59.10
Purchase #6	$181.64	4.821%	$190.3969	$190.40	$190.40	$190.40
Purchase #7	$124.28	3.710%	$128.8908	$128.89	$128.90	$128.90
7 purchase totals =	$1,033.93		$1,077.4406	$1,077.44	$1,077.45	$1,077.50