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 $73.60   3.177%   $75.9383   $75.94   $75.95   $75.90  
  Purchase #2 $155.64   5.837%   $164.7247   $164.72   $164.70   $164.70  
  Purchase #3 $218.32   12.233%   $245.0271   $245.03   $245.05   $245.00  
  Purchase #4 $231.75   11.105%   $257.4858   $257.49   $257.50   $257.50  
  Purchase #5 $212.87   7.804%   $229.4824   $229.48   $229.50   $229.50  
  Purchase #6 $46.81   10.435%   $51.6946   $51.69   $51.70   $51.70  
  Purchase #7 $170.82   6.271%   $181.5321   $181.53   $181.55   $181.50  
  7 purchase totals = $1,109.81       $1,205.8850   $1,205.88   $1,205.95   $1,205.80