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	$73.59	3.734%	$76.3379	$76.34	$76.35	$76.30
Purchase #2	$168.81	6.314%	$179.4687	$179.47	$179.45	$179.50
Purchase #3	$246.28	3.740%	$255.4909	$255.49	$255.50	$255.50
Purchase #4	$92.83	10.798%	$102.8538	$102.85	$102.85	$102.90
Purchase #5	$187.25	13.533%	$212.5905	$212.59	$212.60	$212.60
Purchase #6	$226.81	13.726%	$257.9419	$257.94	$257.95	$257.90
Purchase #7	$61.86	11.428%	$68.9294	$68.93	$68.95	$68.90
7 purchase totals =	$1,057.43		$1,153.6131	$1,153.61	$1,153.65	$1,153.60