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 $114.92   9.257%   $125.5581   $125.56   $125.55   $125.60  
  Purchase #2 $109.81   8.379%   $119.011   $119.01   $119.00   $119.00  
  Purchase #3 $12.63   7.625%   $13.593   $13.59   $13.60   $13.60  
  Purchase #4 $43.73   12.201%   $49.0655   $49.07   $49.05   $49.10  
  Purchase #5 $150.91   6.485%   $160.6965   $160.70   $160.70   $160.70  
  Purchase #6 $10.67   8.806%   $11.6096   $11.61   $11.60   $11.60  
  Purchase #7 $141.29   5.829%   $149.5258   $149.53   $149.55   $149.50  
  7 purchase totals = $583.96       $629.0595   $629.07   $629.05   $629.10