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 $114.50   10.248%   $126.234   $126.23   $126.25   $126.20  
  Purchase #2 $133.95   13.703%   $152.3052   $152.31   $152.30   $152.30  
  Purchase #3 $191.41   6.615%   $204.0718   $204.07   $204.05   $204.10  
  Purchase #4 $170.31   5.275%   $179.2939   $179.29   $179.30   $179.30  
  Purchase #5 $26.82   7.783%   $28.9074   $28.91   $28.90   $28.90  
  Purchase #6 $151.84   8.304%   $164.4488   $164.45   $164.45   $164.40  
  Purchase #7 $118.64   10.134%   $130.663   $130.66   $130.65   $130.70  
  7 purchase totals = $907.47       $985.9241   $985.92   $985.90   $985.90