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 $68.44   10.494%   $75.6221   $75.62   $75.60   $75.60  
  Purchase #2 $191.30   3.208%   $197.4369   $197.44   $197.45   $197.40  
  Purchase #3 $249.43   12.606%   $280.8731   $280.87   $280.85   $280.90  
  Purchase #4 $46.37   6.173%   $49.2324   $49.23   $49.25   $49.20  
  Purchase #5 $132.81   7.290%   $142.4918   $142.49   $142.50   $142.50  
  Purchase #6 $231.59   4.785%   $242.6716   $242.67   $242.65   $242.70  
  Purchase #7 $104.54   10.527%   $115.5449   $115.54   $115.55   $115.50  
  7 purchase totals = $1,024.48       $1,103.8728   $1,103.86   $1,103.85   $1,103.80