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 $194.66   7.441%   $209.1447   $209.14   $209.15   $209.10  
  Purchase #2 $48.88   11.605%   $54.5525   $54.55   $54.55   $54.60  
  Purchase #3 $52.72   9.452%   $57.7031   $57.70   $57.70   $57.70  
  Purchase #4 $49.52   4.544%   $51.7702   $51.77   $51.75   $51.80  
  Purchase #5 $230.87   8.525%   $250.5517   $250.55   $250.55   $250.60  
  Purchase #6 $137.88   7.712%   $148.5133   $148.51   $148.50   $148.50  
  Purchase #7 $248.76   5.596%   $262.6806   $262.68   $262.70   $262.70  
  7 purchase totals = $963.29       $1,034.9161   $1,034.90   $1,034.90   $1,035.00