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 $67.40   12.546%   $75.856   $75.86   $75.85   $75.90  
  Purchase #2 $245.54   5.581%   $259.2436   $259.24   $259.25   $259.20  
  Purchase #3 $27.56   11.820%   $30.8176   $30.82   $30.80   $30.80  
  Purchase #4 $68.35   5.797%   $72.3122   $72.31   $72.30   $72.30  
  Purchase #5 $158.36   3.264%   $163.5289   $163.53   $163.55   $163.50  
  Purchase #6 $214.76   8.792%   $233.6417   $233.64   $233.65   $233.60  
  Purchase #7 $168.62   11.635%   $188.2389   $188.24   $188.25   $188.20  
  7 purchase totals = $950.59       $1,023.6389   $1,023.64   $1,023.65   $1,023.50