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	$237.87	8.821%	$258.8525	$258.85	$258.85	$258.90
Purchase #2	$242.28	6.313%	$257.5751	$257.58	$257.60	$257.60
Purchase #3	$147.37	5.342%	$155.2425	$155.24	$155.25	$155.20
Purchase #4	$7.40	4.853%	$7.7591	$7.76	$7.75	$7.80
Purchase #5	$40.61	6.468%	$43.2367	$43.24	$43.25	$43.20
Purchase #6	$85.46	5.626%	$90.268	$90.27	$90.25	$90.30
Purchase #7	$43.88	8.143%	$47.4531	$47.45	$47.45	$47.50
7 purchase totals =	$804.87		$860.3870	$860.39	$860.40	$860.50