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 $116.46   7.862%   $125.6161   $125.62   $125.60   $125.60  
  Purchase #2 $24.63   5.314%   $25.9388   $25.94   $25.95   $25.90  
  Purchase #3 $241.70   6.432%   $257.2461   $257.25   $257.25   $257.20  
  Purchase #4 $23.86   6.577%   $25.4293   $25.43   $25.45   $25.40  
  Purchase #5 $91.95   3.260%   $94.9476   $94.95   $94.95   $94.90  
  Purchase #6 $219.87   11.605%   $245.3859   $245.39   $245.40   $245.40  
  Purchase #7 $192.35   13.258%   $217.8518   $217.85   $217.85   $217.90  
  7 purchase totals = $910.82       $992.4156   $992.43   $992.45   $992.30