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 $82.51   13.859%   $93.9451   $93.95   $93.95   $93.90  
  Purchase #2 $62.57   10.549%   $69.1705   $69.17   $69.15   $69.20  
  Purchase #3 $178.55   4.105%   $185.8795   $185.88   $185.90   $185.90  
  Purchase #4 $32.98   11.664%   $36.8268   $36.83   $36.85   $36.80  
  Purchase #5 $116.50   12.544%   $131.1138   $131.11   $131.10   $131.10  
  Purchase #6 $240.46   9.664%   $263.6981   $263.70   $263.70   $263.70  
  Purchase #7 $209.45   10.434%   $231.304   $231.30   $231.30   $231.30  
  7 purchase totals = $923.02       $1,011.9378   $1,011.94   $1,011.95   $1,011.90