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 $245.99   5.710%   $260.036   $260.04   $260.05   $260.00  
  Purchase #2 $73.44   13.410%   $83.2883   $83.29   $83.30   $83.30  
  Purchase #3 $149.74   6.425%   $159.3608   $159.36   $159.35   $159.40  
  Purchase #4 $171.76   4.360%   $179.2487   $179.25   $179.25   $179.20  
  Purchase #5 $110.26   3.570%   $114.1963   $114.20   $114.20   $114.20  
  Purchase #6 $249.95   7.322%   $268.2513   $268.25   $268.25   $268.30  
  Purchase #7 $92.93   12.835%   $104.8576   $104.86   $104.85   $104.90  
  7 purchase totals = $1,094.07       $1,169.2390   $1,169.25   $1,169.25   $1,169.30