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 $113.94   10.294%   $125.669   $125.67   $125.65   $125.70  
  Purchase #2 $117.46   6.311%   $124.8729   $124.87   $124.85   $124.90  
  Purchase #3 $207.39   10.115%   $228.3675   $228.37   $228.35   $228.40  
  Purchase #4 $143.83   12.287%   $161.5024   $161.50   $161.50   $161.50  
  Purchase #5 $85.89   5.432%   $90.5555   $90.56   $90.55   $90.60  
  Purchase #6 $67.82   13.236%   $76.7967   $76.80   $76.80   $76.80  
  Purchase #7 $43.49   3.805%   $45.1448   $45.14   $45.15   $45.10  
  7 purchase totals = $779.82       $852.9088   $852.91   $852.85   $853.00