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 $105.58   8.280%   $114.322   $114.32   $114.30   $114.30  
  Purchase #2 $242.80   12.857%   $274.0168   $274.02   $274.00   $274.00  
  Purchase #3 $158.26   5.241%   $166.5544   $166.55   $166.55   $166.60  
  Purchase #4 $191.29   4.236%   $199.393   $199.39   $199.40   $199.40  
  Purchase #5 $90.53   4.321%   $94.4418   $94.44   $94.45   $94.40  
  Purchase #6 $135.46   12.712%   $152.6797   $152.68   $152.70   $152.70  
  Purchase #7 $156.60   7.372%   $168.1446   $168.14   $168.15   $168.10  
  7 purchase totals = $1,080.52       $1,169.5523   $1,169.54   $1,169.55   $1,169.50