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 $58.32   4.505%   $60.9473   $60.95   $60.95   $60.90  
  Purchase #2 $153.26   5.489%   $161.6724   $161.67   $161.65   $161.70  
  Purchase #3 $16.68   5.114%   $17.533   $17.53   $17.55   $17.50  
  Purchase #4 $206.56   4.509%   $215.8738   $215.87   $215.85   $215.90  
  Purchase #5 $176.95   5.832%   $187.2697   $187.27   $187.25   $187.30  
  Purchase #6 $180.95   10.778%   $200.4528   $200.45   $200.45   $200.50  
  Purchase #7 $36.89   5.398%   $38.8813   $38.88   $38.90   $38.90  
  7 purchase totals = $829.61       $882.6303   $882.62   $882.60   $882.70