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	$128.39	10.646%	$142.0584	$142.06	$142.05	$142.10
Purchase #2	$203.96	9.363%	$223.0568	$223.06	$223.05	$223.10
Purchase #3	$72.30	6.133%	$76.7342	$76.73	$76.75	$76.70
Purchase #4	$13.87	12.602%	$15.6179	$15.62	$15.60	$15.60
Purchase #5	$217.81	4.286%	$227.1453	$227.15	$227.15	$227.10
Purchase #6	$179.50	9.255%	$196.1127	$196.11	$196.10	$196.10
Purchase #7	$224.60	11.869%	$251.2578	$251.26	$251.25	$251.30
7 purchase totals =	$1,040.43		$1,131.9831	$1,131.99	$1,131.95	$1,132.00