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 $60.84   10.526%   $67.244   $67.24   $67.25   $67.20  
  Purchase #2 $110.76   13.686%   $125.9186   $125.92   $125.90   $125.90  
  Purchase #3 $201.93   10.566%   $223.2659   $223.27   $223.25   $223.30  
  Purchase #4 $63.84   11.519%   $71.1937   $71.19   $71.20   $71.20  
  Purchase #5 $221.27   13.411%   $250.9445   $250.94   $250.95   $250.90  
  Purchase #6 $222.42   5.806%   $235.3337   $235.33   $235.35   $235.30  
  Purchase #7 $129.76   12.874%   $146.4653   $146.47   $146.45   $146.50  
  7 purchase totals = $1,010.82       $1,120.3657   $1,120.36   $1,120.35   $1,120.30