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 $41.93   6.516%   $44.6622   $44.66   $44.65   $44.70  
  Purchase #2 $114.31   4.736%   $119.7237   $119.72   $119.70   $119.70  
  Purchase #3 $159.63   3.179%   $164.7046   $164.70   $164.70   $164.70  
  Purchase #4 $230.38   13.106%   $260.5736   $260.57   $260.55   $260.60  
  Purchase #5 $94.40   3.431%   $97.6389   $97.64   $97.65   $97.60  
  Purchase #6 $222.50   13.105%   $251.6586   $251.66   $251.65   $251.70  
  Purchase #7 $245.82   3.624%   $254.7285   $254.73   $254.75   $254.70  
  7 purchase totals = $1,108.97       $1,193.6901   $1,193.68   $1,193.65   $1,193.70