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 $58.44   5.460%   $61.6308   $61.63   $61.65   $61.60  
  Purchase #2 $238.88   12.473%   $268.6755   $268.68   $268.70   $268.70  
  Purchase #3 $141.37   5.318%   $148.8881   $148.89   $148.90   $148.90  
  Purchase #4 $152.67   12.492%   $171.7415   $171.74   $171.75   $171.70  
  Purchase #5 $97.36   5.284%   $102.5045   $102.50   $102.50   $102.50  
  Purchase #6 $97.30   5.870%   $103.0115   $103.01   $103.00   $103.00  
  Purchase #7 $30.84   4.199%   $32.135   $32.14   $32.15   $32.10  
  7 purchase totals = $816.86       $888.5869   $888.59   $888.65   $888.50