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 $117.95   6.496%   $125.612   $125.61   $125.60   $125.60  
  Purchase #2 $91.73   5.822%   $97.0705   $97.07   $97.05   $97.10  
  Purchase #3 $114.79   4.129%   $119.5297   $119.53   $119.55   $119.50  
  Purchase #4 $212.78   7.463%   $228.6598   $228.66   $228.65   $228.70  
  Purchase #5 $99.54   3.557%   $103.0806   $103.08   $103.10   $103.10  
  Purchase #6 $73.87   12.156%   $82.8496   $82.85   $82.85   $82.80  
  Purchase #7 $116.55   8.868%   $126.8857   $126.89   $126.90   $126.90  
  7 purchase totals = $827.21       $883.6879   $883.69   $883.70   $883.70