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 $55.40   12.419%   $62.2801   $62.28   $62.30   $62.30  
  Purchase #2 $214.47   9.661%   $235.1899   $235.19   $235.20   $235.20  
  Purchase #3 $188.42   3.595%   $195.1937   $195.19   $195.20   $195.20  
  Purchase #4 $40.43   10.496%   $44.6735   $44.67   $44.65   $44.70  
  Purchase #5 $93.81   6.226%   $99.6506   $99.65   $99.65   $99.70  
  Purchase #6 $187.87   10.144%   $206.9275   $206.93   $206.95   $206.90  
  Purchase #7 $72.59   13.714%   $82.545   $82.55   $82.55   $82.50  
  7 purchase totals = $852.99       $926.4603   $926.46   $926.50   $926.50