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 $24.58   5.643%   $25.967   $25.97   $25.95   $26.00  
  Purchase #2 $235.61   7.726%   $253.8132   $253.81   $253.80   $253.80  
  Purchase #3 $38.81   13.821%   $44.1739   $44.17   $44.15   $44.20  
  Purchase #4 $56.97   7.617%   $61.3094   $61.31   $61.30   $61.30  
  Purchase #5 $120.53   9.695%   $132.2154   $132.22   $132.20   $132.20  
  Purchase #6 $241.58   8.309%   $261.6529   $261.65   $261.65   $261.70  
  Purchase #7 $228.65   10.553%   $252.7794   $252.78   $252.80   $252.80  
  7 purchase totals = $946.73       $1,031.9112   $1,031.91   $1,031.85   $1,032.00