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 $112.76   11.739%   $125.9969   $126.00   $126.00   $126.00  
  Purchase #2 $31.47   11.526%   $35.0972   $35.10   $35.10   $35.10  
  Purchase #3 $76.93   4.700%   $80.5457   $80.55   $80.55   $80.50  
  Purchase #4 $233.83   10.172%   $257.6152   $257.62   $257.60   $257.60  
  Purchase #5 $110.99   5.801%   $117.4285   $117.43   $117.45   $117.40  
  Purchase #6 $184.38   12.398%   $207.2394   $207.24   $207.25   $207.20  
  Purchase #7 $186.77   4.759%   $195.6584   $195.66   $195.65   $195.70  
  7 purchase totals = $937.13       $1,019.5813   $1,019.60   $1,019.60   $1,019.50