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	$155.86	8.625%	$169.3029	$169.30	$169.30	$169.30
Purchase #2	$249.75	8.340%	$270.5792	$270.58	$270.60	$270.60
Purchase #3	$95.91	10.319%	$105.807	$105.81	$105.80	$105.80
Purchase #4	$11.82	6.132%	$12.5448	$12.54	$12.55	$12.50
Purchase #5	$43.49	9.266%	$47.5198	$47.52	$47.50	$47.50
Purchase #6	$239.94	6.715%	$256.052	$256.05	$256.05	$256.10
Purchase #7	$38.28	4.742%	$40.0952	$40.10	$40.10	$40.10
7 purchase totals =	$835.05		$901.9009	$901.90	$901.90	$901.90