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 $241.83   8.479%   $262.3348   $262.33   $262.35   $262.30  
  Purchase #2 $138.71   7.732%   $149.4351   $149.44   $149.45   $149.40  
  Purchase #3 $165.37   5.445%   $174.3744   $174.37   $174.35   $174.40  
  Purchase #4 $110.76   10.672%   $122.5803   $122.58   $122.60   $122.60  
  Purchase #5 $125.38   11.262%   $139.5003   $139.50   $139.50   $139.50  
  Purchase #6 $170.35   10.161%   $187.6593   $187.66   $187.65   $187.70  
  Purchase #7 $119.59   11.326%   $133.1348   $133.13   $133.15   $133.10  
  7 purchase totals = $1,071.99       $1,169.0190   $1,169.01   $1,169.05   $1,169.00