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	$187.86	4.703%	$196.6951	$196.70	$196.70	$196.70
Purchase #2	$147.81	11.274%	$164.4741	$164.47	$164.45	$164.50
Purchase #3	$56.95	11.195%	$63.3256	$63.33	$63.35	$63.30
Purchase #4	$37.33	9.418%	$40.8457	$40.85	$40.85	$40.80
Purchase #5	$63.71	10.275%	$70.2562	$70.26	$70.25	$70.30
Purchase #6	$49.37	6.431%	$52.545	$52.55	$52.55	$52.50
Purchase #7	$151.87	5.691%	$160.5129	$160.51	$160.50	$160.50
7 purchase totals =	$694.90		$748.6546	$748.67	$748.65	$748.60