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 $68.32   10.670%   $75.6097   $75.61   $75.60   $75.60  
  Purchase #2 $248.86   4.115%   $259.1006   $259.10   $259.10   $259.10  
  Purchase #3 $179.86   7.555%   $193.4484   $193.45   $193.45   $193.40  
  Purchase #4 $242.68   11.513%   $270.6197   $270.62   $270.60   $270.60  
  Purchase #5 $31.73   6.711%   $33.8594   $33.86   $33.85   $33.90  
  Purchase #6 $239.40   7.183%   $256.5961   $256.60   $256.60   $256.60  
  Purchase #7 $104.46   5.442%   $110.1447   $110.14   $110.15   $110.10  
  7 purchase totals = $1,115.31       $1,199.3786   $1,199.38   $1,199.35   $1,199.30