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 $86.67   10.333%   $95.6256   $95.63   $95.65   $95.60  
  Purchase #2 $67.81   13.778%   $77.1529   $77.15   $77.15   $77.20  
  Purchase #3 $113.27   13.126%   $128.1378   $128.14   $128.15   $128.10  
  Purchase #4 $54.93   4.843%   $57.5903   $57.59   $57.60   $57.60  
  Purchase #5 $190.89   9.734%   $209.4712   $209.47   $209.45   $209.50  
  Purchase #6 $205.63   10.300%   $226.8099   $226.81   $226.80   $226.80  
  Purchase #7 $18.67   5.466%   $19.6905   $19.69   $19.70   $19.70  
  7 purchase totals = $737.87       $814.4782   $814.48   $814.50   $814.50