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 $55.76   11.262%   $62.0397   $62.04   $62.05   $62.00  
  Purchase #2 $223.40   11.591%   $249.2943   $249.29   $249.30   $249.30  
  Purchase #3 $163.75   11.166%   $182.0343   $182.03   $182.05   $182.00  
  Purchase #4 $97.59   10.709%   $108.0409   $108.04   $108.05   $108.00  
  Purchase #5 $86.41   8.561%   $93.8076   $93.81   $93.80   $93.80  
  Purchase #6 $153.53   11.282%   $170.8513   $170.85   $170.85   $170.90  
  Purchase #7 $216.38   6.161%   $229.7112   $229.71   $229.70   $229.70  
  7 purchase totals = $996.82       $1,095.7793   $1,095.77   $1,095.80   $1,095.70