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 $90.41   4.738%   $94.6936   $94.69   $94.70   $94.70  
  Purchase #2 $114.67   9.865%   $125.9822   $125.98   $126.00   $126.00  
  Purchase #3 $152.66   3.484%   $157.9787   $157.98   $158.00   $158.00  
  Purchase #4 $250.60   5.177%   $263.5736   $263.57   $263.55   $263.60  
  Purchase #5 $91.81   11.580%   $102.4416   $102.44   $102.45   $102.40  
  Purchase #6 $242.73   9.539%   $265.884   $265.88   $265.90   $265.90  
  Purchase #7 $41.73   9.331%   $45.6238   $45.62   $45.60   $45.60  
  7 purchase totals = $984.61       $1,056.1775   $1,056.16   $1,056.20   $1,056.20