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 $216.95   3.360%   $224.2395   $224.24   $224.25   $224.20  
  Purchase #2 $61.84   8.150%   $66.88   $66.88   $66.90   $66.90  
  Purchase #3 $179.37   6.859%   $191.673   $191.67   $191.65   $191.70  
  Purchase #4 $144.61   13.381%   $163.9603   $163.96   $163.95   $164.00  
  Purchase #5 $51.25   8.729%   $55.7236   $55.72   $55.70   $55.70  
  Purchase #6 $136.29   9.242%   $148.8859   $148.89   $148.90   $148.90  
  Purchase #7 $186.80   8.333%   $202.366   $202.37   $202.35   $202.40  
  7 purchase totals = $977.11       $1,053.7283   $1,053.73   $1,053.70   $1,053.80