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 $207.60   10.765%   $229.9481   $229.95   $229.95   $229.90  
  Purchase #2 $66.82   8.360%   $72.4062   $72.41   $72.40   $72.40  
  Purchase #3 $175.87   11.405%   $195.928   $195.93   $195.95   $195.90  
  Purchase #4 $198.72   3.284%   $205.246   $205.25   $205.25   $205.20  
  Purchase #5 $154.31   5.290%   $162.473   $162.47   $162.45   $162.50  
  Purchase #6 $16.34   9.420%   $17.8792   $17.88   $17.90   $17.90  
  Purchase #7 $95.32   6.347%   $101.37   $101.37   $101.35   $101.40  
  7 purchase totals = $914.98       $985.2505   $985.26   $985.25   $985.20