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 $172.66   13.646%   $196.2212   $196.22   $196.20   $196.20  
  Purchase #2 $123.80   8.810%   $134.7068   $134.71   $134.70   $134.70  
  Purchase #3 $172.43   9.431%   $188.6919   $188.69   $188.70   $188.70  
  Purchase #4 $124.65   7.688%   $134.2331   $134.23   $134.25   $134.20  
  Purchase #5 $60.53   9.797%   $66.4601   $66.46   $66.45   $66.50  
  Purchase #6 $167.80   6.704%   $179.0493   $179.05   $179.05   $179.00  
  Purchase #7 $137.48   7.677%   $148.0343   $148.03   $148.05   $148.00  
  7 purchase totals = $959.35       $1,047.3967   $1,047.39   $1,047.40   $1,047.30