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 $52.57   11.158%   $58.4358   $58.44   $58.45   $58.40  
  Purchase #2 $195.87   6.225%   $208.0629   $208.06   $208.05   $208.10  
  Purchase #3 $188.85   13.617%   $214.5657   $214.57   $214.55   $214.60  
  Purchase #4 $178.55   9.291%   $195.1391   $195.14   $195.15   $195.10  
  Purchase #5 $90.52   9.810%   $99.4   $99.40   $99.40   $99.40  
  Purchase #6 $182.35   9.635%   $199.9194   $199.92   $199.90   $199.90  
  Purchase #7 $148.50   6.148%   $157.6298   $157.63   $157.65   $157.60  
  7 purchase totals = $1,037.21       $1,133.1527   $1,133.16   $1,133.15   $1,133.10