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	$68.51	4.436%	$71.5491	$71.55	$71.55	$71.50
Purchase #2	$68.32	12.516%	$76.8709	$76.87	$76.85	$76.90
Purchase #3	$134.35	6.299%	$142.8127	$142.81	$142.80	$142.80
Purchase #4	$223.35	4.622%	$233.6732	$233.67	$233.65	$233.70
Purchase #5	$97.25	7.381%	$104.428	$104.43	$104.45	$104.40
Purchase #6	$53.75	13.732%	$61.131	$61.13	$61.15	$61.10
Purchase #7	$224.91	13.420%	$255.0929	$255.09	$255.10	$255.10
7 purchase totals =	$870.44		$945.5578	$945.55	$945.55	$945.50