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 $59.94   4.590%   $62.6912   $62.69   $62.70   $62.70  
  Purchase #2 $84.28   8.631%   $91.5542   $91.55   $91.55   $91.60  
  Purchase #3 $76.83   4.687%   $80.431   $80.43   $80.45   $80.40  
  Purchase #4 $73.56   9.556%   $80.5894   $80.59   $80.60   $80.60  
  Purchase #5 $210.93   3.147%   $217.568   $217.57   $217.55   $217.60  
  Purchase #6 $182.82   3.171%   $188.6172   $188.62   $188.60   $188.60  
  Purchase #7 $179.93   12.759%   $202.8873   $202.89   $202.90   $202.90  
  7 purchase totals = $868.29       $924.3383   $924.34   $924.35   $924.40