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 $61.47   6.502%   $65.4668   $65.47   $65.45   $65.50  
  Purchase #2 $218.27   7.315%   $234.2365   $234.24   $234.25   $234.20  
  Purchase #3 $238.63   11.455%   $265.9651   $265.97   $265.95   $266.00  
  Purchase #4 $79.84   8.726%   $86.8068   $86.81   $86.80   $86.80  
  Purchase #5 $83.45   8.709%   $90.7177   $90.72   $90.70   $90.70  
  Purchase #6 $217.67   6.243%   $231.2591   $231.26   $231.25   $231.30  
  Purchase #7 $170.86   13.232%   $193.4682   $193.47   $193.45   $193.50  
  7 purchase totals = $1,070.19       $1,167.9202   $1,167.94   $1,167.85   $1,168.00