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 $215.84   13.610%   $245.2158   $245.22   $245.20   $245.20  
  Purchase #2 $95.57   9.533%   $104.6807   $104.68   $104.70   $104.70  
  Purchase #3 $164.38   11.189%   $182.7725   $182.77   $182.75   $182.80  
  Purchase #4 $154.90   4.515%   $161.8937   $161.89   $161.90   $161.90  
  Purchase #5 $126.40   4.215%   $131.7278   $131.73   $131.75   $131.70  
  Purchase #6 $161.69   9.331%   $176.7773   $176.78   $176.80   $176.80  
  Purchase #7 $95.76   6.751%   $102.2248   $102.22   $102.20   $102.20  
  7 purchase totals = $1,014.54       $1,105.2926   $1,105.29   $1,105.30   $1,105.30