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 $118.34   5.767%   $125.1647   $125.16   $125.15   $125.20  
  Purchase #2 $87.52   6.162%   $92.913   $92.91   $92.90   $92.90  
  Purchase #3 $240.29   13.298%   $272.2438   $272.24   $272.25   $272.20  
  Purchase #4 $245.97   6.475%   $261.8966   $261.90   $261.90   $261.90  
  Purchase #5 $117.66   6.356%   $125.1385   $125.14   $125.15   $125.10  
  Purchase #6 $32.70   11.300%   $36.3951   $36.40   $36.40   $36.40  
  Purchase #7 $216.52   7.378%   $232.4948   $232.49   $232.50   $232.50  
  7 purchase totals = $1,059.00       $1,146.2465   $1,146.24   $1,146.25   $1,146.20