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 $177.93   10.553%   $196.707   $196.71   $196.70   $196.70  
  Purchase #2 $92.79   10.824%   $102.8336   $102.83   $102.85   $102.80  
  Purchase #3 $71.37   10.134%   $78.6026   $78.60   $78.60   $78.60  
  Purchase #4 $163.86   13.591%   $186.1302   $186.13   $186.15   $186.10  
  Purchase #5 $49.66   4.450%   $51.8699   $51.87   $51.85   $51.90  
  Purchase #6 $94.41   4.551%   $98.7066   $98.71   $98.70   $98.70  
  Purchase #7 $185.79   8.753%   $202.0522   $202.05   $202.05   $202.10  
  7 purchase totals = $835.81       $916.9021   $916.90   $916.90   $916.90