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 $195.63   3.223%   $201.9352   $201.94   $201.95   $201.90  
  Purchase #2 $202.38   9.433%   $221.4705   $221.47   $221.45   $221.50  
  Purchase #3 $38.68   5.320%   $40.7378   $40.74   $40.75   $40.70  
  Purchase #4 $189.28   3.673%   $196.2323   $196.23   $196.25   $196.20  
  Purchase #5 $65.70   11.812%   $73.4605   $73.46   $73.45   $73.50  
  Purchase #6 $89.55   5.744%   $94.6938   $94.69   $94.70   $94.70  
  Purchase #7 $48.96   10.689%   $54.1933   $54.19   $54.20   $54.20  
  7 purchase totals = $830.18       $882.7234   $882.72   $882.75   $882.70