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 $32.66   5.849%   $34.5703   $34.57   $34.55   $34.60  
  Purchase #2 $237.59   10.544%   $262.6415   $262.64   $262.65   $262.60  
  Purchase #3 $89.73   4.276%   $93.5669   $93.57   $93.55   $93.60  
  Purchase #4 $247.50   11.397%   $275.7076   $275.71   $275.70   $275.70  
  Purchase #5 $8.53   10.486%   $9.4245   $9.42   $9.40   $9.40  
  Purchase #6 $195.80   11.179%   $217.6885   $217.69   $217.70   $217.70  
  Purchase #7 $230.53   4.429%   $240.7402   $240.74   $240.75   $240.70  
  7 purchase totals = $1,042.34       $1,134.3395   $1,134.34   $1,134.30   $1,134.30