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 $114.68   9.301%   $125.3464   $125.35   $125.35   $125.30  
  Purchase #2 $171.44   12.606%   $193.0517   $193.05   $193.05   $193.10  
  Purchase #3 $135.38   10.376%   $149.427   $149.43   $149.45   $149.40  
  Purchase #4 $144.52   13.850%   $164.536   $164.54   $164.55   $164.50  
  Purchase #5 $176.92   5.416%   $186.502   $186.50   $186.50   $186.50  
  Purchase #6 $97.82   6.758%   $104.4307   $104.43   $104.45   $104.40  
  Purchase #7 $153.98   10.621%   $170.3342   $170.33   $170.35   $170.30  
  7 purchase totals = $994.74       $1,093.6280   $1,093.63   $1,093.70   $1,093.50