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 $210.37   11.676%   $234.9328   $234.93   $234.95   $234.90  
  Purchase #2 $57.86   8.702%   $62.895   $62.90   $62.90   $62.90  
  Purchase #3 $149.85   7.799%   $161.5368   $161.54   $161.55   $161.50  
  Purchase #4 $98.74   11.336%   $109.9332   $109.93   $109.95   $109.90  
  Purchase #5 $101.67   10.216%   $112.0566   $112.06   $112.05   $112.10  
  Purchase #6 $230.76   13.183%   $261.1811   $261.18   $261.20   $261.20  
  Purchase #7 $215.25   6.219%   $228.6364   $228.64   $228.65   $228.60  
  7 purchase totals = $1,064.50       $1,171.1719   $1,171.18   $1,171.25   $1,171.10