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 $104.68   9.653%   $114.7848   $114.78   $114.80   $114.80  
  Purchase #2 $237.51   3.409%   $245.6067   $245.61   $245.60   $245.60  
  Purchase #3 $218.99   4.590%   $229.0416   $229.04   $229.05   $229.00  
  Purchase #4 $109.55   8.867%   $119.2638   $119.26   $119.25   $119.30  
  Purchase #5 $245.66   4.729%   $257.2773   $257.28   $257.30   $257.30  
  Purchase #6 $123.34   6.532%   $131.3966   $131.40   $131.40   $131.40  
  Purchase #7 $95.53   12.528%   $107.498   $107.50   $107.50   $107.50  
  7 purchase totals = $1,135.26       $1,204.8688   $1,204.87   $1,204.90   $1,204.90