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 $119.80   5.556%   $126.4561   $126.46   $126.45   $126.50  
  Purchase #2 $217.64   3.336%   $224.9005   $224.90   $224.90   $224.90  
  Purchase #3 $48.78   12.756%   $55.0024   $55.00   $55.00   $55.00  
  Purchase #4 $34.44   4.686%   $36.0539   $36.05   $36.05   $36.10  
  Purchase #5 $175.55   7.143%   $188.0895   $188.09   $188.10   $188.10  
  Purchase #6 $153.75   13.654%   $174.743   $174.74   $174.75   $174.70  
  Purchase #7 $216.99   5.235%   $228.3494   $228.35   $228.35   $228.30  
  7 purchase totals = $966.95       $1,033.5948   $1,033.59   $1,033.60   $1,033.60