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 $52.47   5.532%   $55.3726   $55.37   $55.35   $55.40  
  Purchase #2 $230.43   7.219%   $247.0647   $247.06   $247.05   $247.10  
  Purchase #3 $188.63   5.601%   $199.1952   $199.20   $199.20   $199.20  
  Purchase #4 $63.55   3.756%   $65.9369   $65.94   $65.95   $65.90  
  Purchase #5 $237.73   7.451%   $255.4433   $255.44   $255.45   $255.40  
  Purchase #6 $195.53   11.750%   $218.5048   $218.50   $218.50   $218.50  
  Purchase #7 $149.95   9.260%   $163.8354   $163.84   $163.85   $163.80  
  7 purchase totals = $1,118.29       $1,205.3529   $1,205.35   $1,205.35   $1,205.30