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 $66.65   8.823%   $72.5305   $72.53   $72.55   $72.50  
  Purchase #2 $69.81   5.771%   $73.8387   $73.84   $73.85   $73.80  
  Purchase #3 $152.63   4.282%   $159.1656   $159.17   $159.15   $159.20  
  Purchase #4 $188.96   6.727%   $201.6713   $201.67   $201.65   $201.70  
  Purchase #5 $114.82   9.548%   $125.783   $125.78   $125.80   $125.80  
  Purchase #6 $146.48   5.768%   $154.929   $154.93   $154.95   $154.90  
  Purchase #7 $212.28   12.163%   $238.0996   $238.10   $238.10   $238.10  
  7 purchase totals = $951.63       $1,026.0177   $1,026.02   $1,026.05   $1,026.00