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 $61.95   13.804%   $70.5016   $70.50   $70.50   $70.50  
  Purchase #2 $160.88   4.232%   $167.6884   $167.69   $167.70   $167.70  
  Purchase #3 $182.36   5.246%   $191.9266   $191.93   $191.95   $191.90  
  Purchase #4 $167.94   4.746%   $175.9104   $175.91   $175.90   $175.90  
  Purchase #5 $214.62   11.167%   $238.5866   $238.59   $238.60   $238.60  
  Purchase #6 $70.87   8.874%   $77.159   $77.16   $77.15   $77.20  
  Purchase #7 $5.57   9.810%   $6.1164   $6.12   $6.10   $6.10  
  7 purchase totals = $864.19       $927.8890   $927.90   $927.90   $927.90