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 $195.53   11.817%   $218.6358   $218.64   $218.65   $218.60  
  Purchase #2 $239.68   4.278%   $249.9335   $249.93   $249.95   $249.90  
  Purchase #3 $22.67   10.215%   $24.9857   $24.99   $25.00   $25.00  
  Purchase #4 $223.31   12.840%   $251.983   $251.98   $252.00   $252.00  
  Purchase #5 $237.43   10.212%   $261.6764   $261.68   $261.70   $261.70  
  Purchase #6 $242.51   9.424%   $265.3641   $265.36   $265.35   $265.40  
  Purchase #7 $88.68   11.198%   $98.6104   $98.61   $98.60   $98.60  
  7 purchase totals = $1,249.81       $1,371.1889   $1,371.19   $1,371.25   $1,371.20