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 $51.97   13.429%   $58.9491   $58.95   $58.95   $58.90  
  Purchase #2 $215.87   8.534%   $234.2923   $234.29   $234.30   $234.30  
  Purchase #3 $117.44   5.282%   $123.6432   $123.64   $123.65   $123.60  
  Purchase #4 $150.43   5.304%   $158.4088   $158.41   $158.40   $158.40  
  Purchase #5 $87.37   6.516%   $93.063   $93.06   $93.05   $93.10  
  Purchase #6 $228.43   11.838%   $255.4715   $255.47   $255.45   $255.50  
  Purchase #7 $158.78   13.825%   $180.7313   $180.73   $180.75   $180.70  
  7 purchase totals = $1,010.29       $1,104.5592   $1,104.55   $1,104.55   $1,104.50