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 $113.27   10.511%   $125.1758   $125.18   $125.20   $125.20  
  Purchase #2 $23.59   13.116%   $26.6841   $26.68   $26.70   $26.70  
  Purchase #3 $181.46   12.239%   $203.6689   $203.67   $203.65   $203.70  
  Purchase #4 $231.26   12.375%   $259.8784   $259.88   $259.90   $259.90  
  Purchase #5 $82.45   13.200%   $93.3334   $93.33   $93.35   $93.30  
  Purchase #6 $120.41   12.229%   $135.1349   $135.13   $135.15   $135.10  
  Purchase #7 $75.60   7.304%   $81.1218   $81.12   $81.10   $81.10  
  7 purchase totals = $828.04       $924.9973   $924.99   $925.05   $925.00