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 $56.94   8.873%   $61.9923   $61.99   $62.00   $62.00  
  Purchase #2 $38.65   8.326%   $41.868   $41.87   $41.85   $41.90  
  Purchase #3 $150.43   13.443%   $170.6523   $170.65   $170.65   $170.70  
  Purchase #4 $223.96   7.684%   $241.1691   $241.17   $241.15   $241.20  
  Purchase #5 $23.69   12.395%   $26.6264   $26.63   $26.65   $26.60  
  Purchase #6 $81.43   5.870%   $86.2099   $86.21   $86.20   $86.20  
  Purchase #7 $233.79   9.566%   $256.1544   $256.15   $256.15   $256.20  
  7 purchase totals = $808.89       $884.6724   $884.67   $884.65   $884.80