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	$69.61	4.225%	$72.551	$72.55	$72.55	$72.60
Purchase #2	$30.82	11.438%	$34.3452	$34.35	$34.35	$34.30
Purchase #3	$116.81	5.681%	$123.446	$123.45	$123.45	$123.40
Purchase #4	$117.25	5.718%	$123.9544	$123.95	$123.95	$124.00
Purchase #5	$68.76	13.647%	$78.1437	$78.14	$78.15	$78.10
Purchase #6	$6.53	6.791%	$6.9735	$6.97	$6.95	$7.00
Purchase #7	$168.46	12.547%	$189.5967	$189.60	$189.60	$189.60
7 purchase totals =	$578.24		$629.0105	$629.01	$629.00	$629.00